[MLIR] Use IntValidAlignment for alignment attributes (#158137)

This PR refactors alignment validation in MLIR's MemRef and SPIRV
dialects:
- Use `IntValidAlignment` for consistent type safety across MemRef and
SPIRV dialects
  - Eliminate duplicate validation logic in `MemRefOps.cpp`
  - Adjust error messages in `invalid.mlir` to match improved validation

This is the first of two PRs addressing issue #155677.
GitOrigin-RevId: 33c33d0e0d143fb6197f191921d2b6e4470855da