Enable uint8/int8 mkldnn/dense tensor conversion (#102965)
**Summary**
Support mkldnn tensor and dense tensor conversion with uint8/int8 data type.
**Test Plan**
```
python -m pytest -s -v test_mkldnn.py -k test_conversion_byte_char
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102965
Approved by: https://github.com/jgong5, https://github.com/XiaobingSuper
