[MPS] Implement `polar` via metal shader (#107324)
Use `view_as_real` to cast complex into a pair of floats and then it becomes just another binary operator.
Enable `polar` and `view_as_complex` consistency tests, but skip `test_output_grad_match_polar_cpu` as `mul` operator is yet not supported
Remove redundant `#ifdef __OBJC__` and capture and re-throw exceptions captured during `createCacheBlock` block.
Fixes https://github.com/pytorch/pytorch/issues/78503
TODOs(in followup PRs):
- Implement backwards (requires complex mul and sgn)
- Measure the perf impact of computing the strides on the fly rather than ahead of time (unrelated to this PR)
Partially addresses https://github.com/pytorch/pytorch/issues/105665
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107324
Approved by: https://github.com/albanD
