Draft: Add aarch64 wheels and tests

[Maegereg]

• Rewrites our package jobs to use a matrix.
• Add an aarch64 package job.
• Add an aarch64 test to the dependency matrix.
• Add aarch64 to the supported architectures and make sure cibuildwheel will build it when appropriate.

You can see a successful test of the refactored build jobs here, and a successful test of the new aarch64 jobs here (I skipped as many jobs as possible in both cases to keep the costs as low as possible).