try the new macos-12-xl runners

[pmeier]

As mentioned in #7507 (comment), the regular macos-12 runners hosted by GitHub Actions are underspecced for our needs. They recently introduced XL variants. PyTorch core is explicitly mentioned in the blog post with cutting down runtime from 1.5 hours to 0.5.

The XL runners are 4 times as expensive as the regular ones. Thus, in the light of the cost discussion in #7507, it is only uncontroversial to use them if we achieve roughly a 4x speed-up and thus keeping the cost equal.

[pytorch-bot]

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❌ 2 New Failures

As of commit e6aa720:

NEW FAILURES - The following jobs have failed:

• unittests (3.8, macos-m1-12) / macos-job (gh)
• unittests (3.9, windows.4xlarge, cpu) / windows-job (gh)

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[pmeier]

Python	0370134 (main)	e6aa720 (PR)	speedup
3.8	1h 33m 16s	55m 17s	1.7x
3.9	1h 41m 29s	1h 5m 8s	1.6x
3.10	1h 44m 30s	1h 3m 27s	1.6x
3.11	1h 19m 4s	46m 44s	1.7x

Roughly 70% speed-up and thus better developer experience, because time to signal is significantly decreased. However, since the cost quadruples, we can't go for this, because ultimately cost would rise.

Maybe we can revisit if we go for #7507.