PEP 11: Promote aarch64-unknown-linux-gnu (gcc, glibc) to tier-1

[diegorusso]

As promised in Discourse (https://discuss.python.org/t/pep-11-proposal-to-promote-aarch64-plaftorms-to-tier-1/44774/29) this is the PR to promote aarch64-unknown-linux-gnu to Tier-1.
Since we enabled Arm runners on Github, we haven't seen any issue with those hence the promotion to Tier 1.

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📚 Documentation preview 📚: https://pep-previews--4215.org.readthedocs.build/

[AA-Turner]

Approving editorially, but note per PEP 11:

To be promoted to a tier, steering council support is required and is expected to be driven by team consensus.

Hence applying the "DO-NOT-MERGE" label to prevent accidental merges before agreement from the steering council.

A

[encukou]

The Steering Council can be reached at https://github.com/python/steering-council/issues
I think the Discourse thread has the necessary consensus, but that's for the SC to judge.

[brettcannon]

Update LGTM, but SC needs to approve before merging as Adam pointed out.

[gpshead]

approving for SC after asking a few of us :)

[diegorusso]

Thanks @gpshead and the whole SC!