Fix the bisect runner breaking the output expectation

[jdelStrother]

The bisect runner sets $stdout & $stderr to a StringIO. If your specs include output.to_stdout_from_any_process or output.to_stderr_from_any_process, CaptureStreamToTempfile would then introduce new errors during the bisect run, failing with can't convert Tempfile into StringIO here

Here's one approach, which instead sets $stdout & $stderr to a Tempfile. WDYT? I know previously we've wanted to avoid adding a dependency on tempfile ... we could instead try fixing this at the rspec-expectations level, though not sure how feasible that is.

[JonRowe]

I would rather fix this in the matcher, as hard as that might be to test, if we go down this route I'd also want to benchmark the performance given I suspect a file is slower than an in memory string

[jdelStrother]

Fair enough. See what you think to rspec/rspec-expectations#1486

[JonRowe]

I'm closing this PR because of my earlier concerns, especially given the comment on the matcher itself about being 30x slower and the ever present desire not to require things, I will continue feedback on the other PR, thanks!