[c10d] Ensure collectives are called with the same dtype for all tensor params. (#84664)
While passing tensors with different dtypes don't crash, they don't produce sensible results.
We see data tearing instead of casting.
It's not clear we want to support transparent casting so, for now, we fail when such input is presented.
Fixes #84525
Fixes #ISSUE_NUMBER
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84664
Approved by: https://github.com/rohan-varma
