Migrate to tox 4

[oerc0122]

• Migrate tox.ini to tox 4
• Remove custom install from tox.ini
• Add test for no C extension.
• Rename phonopy_reader to phonopy-reader for tox support (everywhere needed)
• Add verbose flag to tox's pip install command

[github-actions]

Test Results

    26 files   -     7      26 suites   - 7   2h 21m 28s ⏱️ + 30m 44s
 1 066 tests ±    0   1 060 ✅ ±    0   6 💤 ± 0  0 ❌ ±0 
15 695 runs   - 2 325  15 603 ✅  - 2 311  92 💤  - 14  0 ❌ ±0 

Results for commit 4412373. ± Comparison against base commit fb4549d.

♻️ This comment has been updated with latest results.

[ajjackson]

If switching the extra name from phonopy_reader to phonopy-reader works, please make sure to update the references in import error message and installation docs

[ajjackson]

Shall we defer this to post-release, so that things are roughly in sync with #333 ?

[oerc0122]

Shall we defer this to post-release, so that things are roughly in sync with #333 ?

As we discussed in-person the other week, I think this is for the best.

[ajjackson]

This is looking pretty good except that, bafflingly, the platform constraint is only respected for testenv:py310-minrequirements-linux. py310-no-c (platform = linux: linux) and py310-minrequirements-mac (platform = macos: darwin) are running on every platform.

[ajjackson]

Fixed! This is looking good.

The main concern now is that it requires a different tox version from the release tests, so they can't use the same ci_requirements.txt.

The simplest solution could be to hard-code the tox version in test_release.yml until it is migrated; we don't expect to bump it before it is migrated to tox 4 and using ci_requirements.txt again.