Summary:
Pull Request resolved: https://github.com/pytorch/torchrec/pull/1988

Adding dynamo coverage for KJT methods:
- permute
- split
- regroup_as_dict
- getitem
- todict

split and getitem tests need additional checks (similar to pre slice check).

Extracted those checks into pt2/utils, pt2_checks_tensor_slice.

Reviewed By: PaulZhang12

Differential Revision: D57220897

fbshipit-source-id: 4a6314e6ddbf7b5e5d8ad25f72aa65906cff28d7