Invoke pyroma through the command line

[radarhere]

Resolves #9668

The maintainer of pyroma has declared that it is a command line tool, not a library. This PR updates test_pyroma.py to use subprocess to call it, rather than using the import.

You will notice that I have also removed our code handling rc versions (I don't think we've used this since 3.1.0.rc1) and relaxed the pyroma version requirement (now that the changes from #9116 are gone).

[freakboy3742]

Using subprocess isn't an option for iOS, as Python doesn't support the subprocess module (the same will be true for Android or Emacripten).

If this is the approach that is adopted, the test will need to be skipped - subprocess. _can_fork_exec can be used for a property check.

However, I feel a better approach would be to do this outside the scope of pytest, and run it as a separate post-build check of wheels, rather than try to analyze a wheel while running code in (or adjacent to) that wheel.

[radarhere]

I attempted to run it outside of pytest, but it still triggered a subprocess error on iOS.

[hugovk]

Do we need to run it on all platforms as part of the test suite?

Can we instead put it in tox as part of the lint env?

For example: #9670.