github: migrate to GHA aarch64 runners

[thoughtpolice]

We no longer need to do cross compilation, and these instances seem pretty fast. Enable them everywhere across the board.

Checklist

If applicable:

• I have updated CHANGELOG.md
• I have updated the documentation (README.md, docs/, demos/)
• I have updated the config schema (cli/src/config-schema.json)
• I have added tests to cover my changes

[emilazy]

Perhaps should move all the Macs to AArch64 too? Should be just as easy to build binaries for x86, and the AArch64 runners have Rosetta 2 and thus can handle the tests too; and of course the speed improvement should be even larger.

[thoughtpolice]

How do we cross compile on macOS? We don't even need cross, right? The main reason I haven't done it is just bc I haven't swapped over to my Mac in a while to debug issues.

[emilazy]

It can just be used as a native x86 Darwin machine – could even install a native x86 Rust toolchain. I’d assume cargo --target and so on also just works, though (and would be faster).

[thoughtpolice]

Alright, I'll try that, but I'll do a follow up for it in a separate PR since I might have to hit it with a wrench a few times. I think this is good to go, though.