[MPS] Fix batchnorm forward and backward pass (#94351)
Fixes batchnorm forward/backward pass and layer_norm:
Batchnorm Forward pass:
```
- fix batch_norm_mps_out key
- return 1/sqrt(var+epsilon) instead of var
- return empty tensor for mean and var if train is not enabled
- remove native_batch_norm from block list
```
Batchnorm Backward pass:
```
- add revert caculation for save_var used in backward path
- add backward test for native_batch_norm and _native_batch_norm_legit
```
Layer norm:
```
- remove the duplicate calculation from layer_norm_mps
- enable native_layer_norm backward test
- raise atol rtol for native_layer_norm
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94351
Approved by: https://github.com/razarmehr
