CI: Make macOS Intel required to succeed

[hugovk]

Intel-based macOS aka build_macos aka x86_64-apple-darwin is Tier 1 in PEP 11, which means:

• CI failures block releases.
• Changes which would break the main branch are not allowed to be merged; any breakage should be fixed or reverted immediately.
• All core developers are responsible to keep main, and thus these platforms, working.
• Failures on these platforms block a release.

Let's remove it from the "allowed to fail" list so that it is "required to succeed".

(Windows x86 (32-bit) aka build_win32 aka x86_64-pc-windows-msvc is also Tier 1, but I'm not making it required in this PR because some tests are still flaky.)

---

Also remove EOL Python 3.7 from the list of branches. (Or we probably only need bugfix and newer, 3.11+.)

[vstinner]

Be careful: there is known bug on macOS: #110083

[vstinner]

In terms of performance, the GHA macOS now seem to have good performance, between Linux and Windows:

• Ubuntu: 13 min (tests: Total duration: 11 min 11 sec)
• macOS: 17 min (tests: Total duration: 13 min 28 sec)
• Windows x64: 27 min (tests: Total duration: 22 min 59 sec)

[hugovk]

Be careful: there is known bug on macOS: #110083

Shall we wait until it's fixed?

[vstinner]

Shall we wait until it's fixed?

I didn't check the failure rate. So far, the job was non-voting (didn't block a PR if it failed). I'm tracking too many tests: https://github.com/python/cpython/issues/vstinner :-)

[vstinner]

cc @sobolevn

[miss-islington-app]

Thanks @hugovk for the PR, and @ambv for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11, 3.12.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @hugovk and @ambv, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 5add7a6724cbff6c9f0597f0257b64c4f0978c14 3.12

[miss-islington-app]

Sorry, @hugovk and @ambv, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 5add7a6724cbff6c9f0597f0257b64c4f0978c14 3.11

[bedevere-app]

GH-130299 is a backport of this pull request to the 3.12 branch.