- Build aarch64 wheels on native ubuntu-24.04-arm runners instead of
QEMU emulation (massive speedup on every push/PR).
- Move ppc64le and s390x QEMU builds into a separate job that only
runs on refs/tags/v* and skips tests (still extremely slow under
emulation, but no longer gates regular CI).
- Drop EOL CPython 3.8 builds, which also removes the macOS
x86_64-only-installer warning.
- Include arch in artifact names to make them easier to identify.
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