Add various uninterpreted bit tensor data types (try 2) (#95860)
Summary:
This is a retry of https://github.com/pytorch/pytorch/pull/94992 which was reverted due to CI issues.
This PR adds a set of unintrepreted data types on PyTorch which can be used to implement experimental functionality out of core (think fp8, int4, int16 quant, etc).
@bypass-github-export-checks
Test Plan:
```
python test/test_quantization.py -k TestBits
```
Reviewers:
Subscribers:
Tasks:
Tags:
Fixes #ISSUE_NUMBER
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95860
Approved by: https://github.com/atalman
