Fix ENOENT error when running tests under Rails

Under Ruby 3.3, without this change, running tests under Rails using the `bin/rails test` command fails. The failure can be expressed in two ways. If a whole test file is being run (e.g. `bin/rails test test/models/thing_test.rb`, then it looks like the whole contents of the file are being passed to rdbg:

```
(rdbg) nil
(rdbg) (rdbg) false
(rdbg) (rdbg) eval error: (rdbg)//private/tmp/thing/test/models/thing_test.rb:1: syntax error, unexpected end-of-input, expecting ';' or '\n'
...gTest < ActiveSupport::TestCase
...                               ^
nil
(rdbg) eval error: (rdbg)//private/tmp/thing/test/models/thing_test.rb:1: syntax error, unexpected end-of-input
test "stuff" do
               ^
nil
(rdbg) #<ThingTest:0x000000012409ebe0>
(rdbg) true
(rdbg) eval error: (rdbg)//private/tmp/thing/test/models/thing_test.rb:1: syntax error, unexpected `end'
nil
(rdbg) eval error: (rdbg)//private/tmp/thing/test/models/thing_test.rb:1: syntax error, unexpected `end'
nil
(rdbg) Really quit? [Y/n]
```

If a specific line is passed (e.g. `bin/rails test test/models/thing.rb:4`), then the failure is different:

```
(rdbg) #<Thread:0x000000011eae9c40@DEBUGGER__::SESSION@server /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:179 run> terminated with exception (report_on_exception is true):
/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `gets': No such file or directory @ rb_sysopen - test/models/thing_test.rb:6 (Errno::ENOENT)
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `gets'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `readline'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:78:in `block in readline'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:90:in `block in setup_interrupt'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:1981:in `intercept_trap_sigint'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:83:in `setup_interrupt'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:77:in `readline'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:444:in `wait_command'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:404:in `block in wait_command_loop'
	from <internal:kernel>:187:in `loop'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `wait_command_loop'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:329:in `process_event'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:254:in `session_server_main'
	from /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:212:in `block in activate'
nil
#<Errno::ENOENT: No such file or directory @ rb_sysopen - test/models/thing_test.rb:6>
@@@ #<Thread:0x0000000102a5b308 run>
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:1251:in `backtrace'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:1251:in `block in wait_next_action_'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:1249:in `each'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:1249:in `rescue in wait_next_action_'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:1244:in `wait_next_action_'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:875:in `block in wait_next_action'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:866:in `block in fiber_blocking'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:866:in `blocking'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:866:in `fiber_blocking'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:875:in `wait_next_action'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:320:in `suspend'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:251:in `on_breakpoint'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/breakpoint.rb:69:in `suspend'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/breakpoint.rb:170:in `block in setup'
 > /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:2633:in `debugger'
 > /private/tmp/thing/test/models/thing_test.rb:7:in `block in <class:ThingTest>'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest/test.rb:94:in `block (3 levels) in run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest/test.rb:191:in `capture_exceptions'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest/test.rb:89:in `block (2 levels) in run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:303:in `time_it'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest/test.rb:88:in `block in run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:412:in `on_signal'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest/test.rb:239:in `with_info_handler'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest/test.rb:87:in `run'
 > /Users/james/.gem/ruby/3.3.0/gems/activesupport-7.1.3/lib/active_support/executor/test_helper.rb:5:in `block in run'
 > /Users/james/.gem/ruby/3.3.0/gems/activesupport-7.1.3/lib/active_support/execution_wrapper.rb:105:in `perform'
 > /Users/james/.gem/ruby/3.3.0/gems/activesupport-7.1.3/lib/active_support/executor/test_helper.rb:5:in `run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:1126:in `run_one_method'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:378:in `run_one_method'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:365:in `block (2 levels) in run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:364:in `each'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:364:in `block in run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:412:in `on_signal'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:399:in `with_info_handler'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:363:in `run'
 > /Users/james/.gem/ruby/3.3.0/gems/railties-7.1.3/lib/rails/test_unit/line_filtering.rb:10:in `run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:185:in `block in __run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:185:in `map'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:185:in `__run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:162:in `run'
 > /Users/james/.gem/ruby/3.3.0/gems/minitest-5.21.2/lib/minitest.rb:86:in `block in autorun'
@@@ #<Thread:0x00000001200d30d8 /Users/james/.gem/ruby/3.3.0/gems/activerecord-7.1.3/lib/active_record/connection_adapters/abstract/connection_pool/reaper.rb:42 sleep>
 > /Users/james/.gem/ruby/3.3.0/gems/activerecord-7.1.3/lib/active_record/connection_adapters/abstract/connection_pool/reaper.rb:48:in `sleep'
 > /Users/james/.gem/ruby/3.3.0/gems/activerecord-7.1.3/lib/active_record/connection_adapters/abstract/connection_pool/reaper.rb:48:in `block in spawn_thread'
["DEBUGGER Exception: /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/thread_client.rb:1255", #<Errno::ENOENT: No such file or directory @ rb_sysopen - test/models/thing_test.rb:6>, ["/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `gets'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `gets'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `readline'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:78:in `block in readline'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:90:in `block in setup_interrupt'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:1981:in `intercept_trap_sigint'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:83:in `setup_interrupt'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:77:in `readline'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:444:in `wait_command'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:404:in `block in wait_command_loop'", "<internal:kernel>:187:in `loop'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `wait_command_loop'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:329:in `process_event'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:254:in `session_server_main'", "/Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:212:in `block in activate'"]]
E

Error:
ThingTest#test_stuff:
Errno::ENOENT: No such file or directory @ rb_sysopen - test/models/thing_test.rb:6
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `gets'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `gets'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/console.rb:146:in `readline'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:78:in `block in readline'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:90:in `block in setup_interrupt'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:1981:in `intercept_trap_sigint'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:83:in `setup_interrupt'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/local.rb:77:in `readline'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:444:in `wait_command'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:404:in `block in wait_command_loop'
    <internal:kernel>:187:in `loop'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:403:in `wait_command_loop'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:329:in `process_event'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:254:in `session_server_main'
    /Users/james/.gem/ruby/3.3.0/gems/debug-1.9.1/lib/debug/session.rb:212:in `block in activate'
```

Either way, making this change seems to fix it. The error is very reminiscent of that described in #156, where a similar fix was required.

lib/debug/console.rb

@@ -143,7 +143,7 @@ def history
       rescue LoadError
         def readline prompt
           print prompt
-          gets
+          $stdin.gets
         end
 
         def history