[NO-TICKET] Upgrade to libdatadog 8

**What does this PR do?**

This PR upgrades dd-trace-rb to use libdatadog 8.

Even though there were a few breaking API changes, none of those APIs
were being used in the Ruby profiler, so it's a very minor bump for us.

**Motivation:**

This version includes a number of fixes and tweaks that will finally
enable us to land the crash tracker feature
(#3384).

**Additional Notes:**

I'm opening this PR as a draft as libdatadog 8 is not yet available on
rubygems.org, and I'll come back to re-trigger CI and mark this as
non-draft once it is.

**How to test the change?**

Our existing test coverage includes libdatadog testing, so a green CI
is good here :)

ddtrace.gemspec

@@ -66,7 +66,7 @@ Gem::Specification.new do |spec|
 
   # Used by profiling (and possibly others in the future)
   # When updating the version here, please also update the version in `native_extension_helpers.rb` (and yes we have a test for it)
-  spec.add_dependency 'libdatadog', '~> 7.0.0.1.0'
+  spec.add_dependency 'libdatadog', '~> 8.0.0.1.0'
 
   # used for CI visibility product until the next major version
   spec.add_dependency 'datadog-ci', '~> 0.8.1'

ext/datadog_profiling_native_extension/native_extension_helpers.rb

@@ -15,7 +15,7 @@ module NativeExtensionHelpers
       # The MJIT header was introduced on 2.6 and removed on 3.3; for other Rubies we rely on debase-ruby_core_source
       CAN_USE_MJIT_HEADER = RUBY_VERSION.start_with?('2.6', '2.7', '3.0.', '3.1.', '3.2.')
 
-      LIBDATADOG_VERSION = '~> 7.0.0.1.0'
+      LIBDATADOG_VERSION = '~> 8.0.0.1.0'
 
       def self.fail_install_if_missing_extension?
         ENV[ENV_FAIL_INSTALL_IF_MISSING_EXTENSION].to_s.strip.downcase == 'true'