[DFT][rocFFT] Add regression tests for stride validation and rank handling

[ndingle-arm]

Follow up on #760 by adding regression coverage for the rocFFT behavior changed there.

The tests added in #760 cover the separate test_common.hpp one-past-end fix, but do not exercise the rocFFT validation changes.

Add tests covering:

• A stride layout that was previously accepted incorrectly and is now rejected.
• A non-unit innermost stride requiring the stride multiplier during packed-layout validation.
• A rank-4 descriptor being rejected with oneapi::math::unimplemented.

The tests should explicitly assert the expected commit result rather than treating unimplemented as a skipped compute test.

Since rocFFT is not currently available in CI, consider extracting the stride-validation logic into a hardware-independent helper so the first two cases can run in regular CI. Backend integration tests may remain gated on
ONEMATH_ENABLE_ROCFFT_BACKEND.

Acceptance criteria

• Previously false-accepted stride configuration is rejected.
• Invalid non-unit innermost stride configuration is rejected.
• Rank-4 rocFFT descriptor throws oneapi::math::unimplemented.
• Tests fail when the corresponding fixes from [DFT][rocFFT] Fix out-of-bounds stride handling #760 are reverted.