[mlir][arith] Rename `AtomicRMWKind`'s `maxf` → `maximumf`, `minf` → `minimumf` (#66135)

This patch is part of a larger initiative aimed at fixing floating-point
`max` and `min` operations in MLIR:
https://discourse.llvm.org/t/rfc-fix-floating-point-max-and-min-operations-in-mlir/72671.

This commit renames `maxf` and `minf` enumerators of `AtomicRMWKind`
to better reflect the current naming scheme and the goals of the RFC.