Autodetect hypothesis use and suggest marking as thread-unsafe

[ngoldbaum]

In the vein of #17.

See Quansight-Labs/free-threaded-compatibility#116

[lysnikolaou]

I'm a bit confused. Do you mean that pytest-run-parallel should suggest marking it as thread-unsafe by outputting a message somewhere or that it should do it?

[rgommers]

No message I think, just apply the thread_unsafe marker so any tests using hypothesis are not run in parallel, since that's just as unsafe as, for example, pytest.warns it looks like.

[lysnikolaou]

Got it. I just wanted to make sure we're aligned on that because of the wording "and suggest marking as thread-unsafe" in the issue title.

[ngoldbaum]

Sorry, that was me misunderstanding how pytest-run-parallel handles pytest.warns.