Fix byebug when running tests about brew

[dduugg]

Thanks for taking the time to write this u, and for your add’l investigative work. For the time being, it looks like we can include debug as long as we also pin psych to < 5.

[apainintheneck]

My best guess is that this was caused by #12967 which turned off stdin to avoid flaky tests. We could probably just conditionally include stdin when running tests with --byebug set.

@issyl0 also suggested maybe moving to the debug gem since it's more actively maintained and works better with Ruby 3. It seems like we'd have to figure out how to build the psych gem which has native dependencies to make that work though. @dduugg saw some failures when he tried it locally and @Bo98 suggested that that might be related to how https://github.com/Homebrew/homebrew-portable-ruby gets built.

[MikeMcQuaid]

@issyl0 also suggested maybe moving to the debug gem since it's more actively maintained and works better with Ruby 3.

This seems ideal 👍🏻