[MPS] Fix correctness issues with Pool2D ops (#94348)
- Fix wrong results in AvgPool2D when `count_include_pad=True`
- Fix issues with adaptive average and max pool2d
- Remove the redundant blocking copies from `AdaptiveMaxPool2d`
- Add `divisor` to cached string key to avoid conflicts
- Add test case when both `ceil_mode` and `count_include_pad` are True (previously failed).
- Clean up redundant code
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94348
Approved by: https://github.com/kulinseth
