Rework the internal AtomicOps macro plumbing to generate per-type
implementations from a mapping list.
Capture the trait definition once and reuse it for both declaration
and per-type impl expansion to reduce duplication and keep future
extensions simple.
This is a preparatory refactor for enabling i8/i16 atomics cleanly.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251228120546.1602275-2-fujita.tomonori@gmail.com
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