feat: add PolynomialLR scheduler (#82769)
### Description
<!-- What did you change and why was it needed? -->
Add PolynomialLR scheduler.
### Issue
Closes #79511.
### Testing
I added tests for PolynomialLR.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82769
Approved by: https://github.com/datumbox
