Add various uninterpreted bit tensor data types (#94992)
Summary:
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).
Note: this is a copy-pasta of https://github.com/pytorch/pytorch/pull/89990 with a bug fix for clang9, easier to just to put up another PR since I'm not sure how comandeering works with Meta-only changes.
@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/94992
Approved by: https://github.com/angelayi
