Optimize to if the datatyep of the source tensor is as same as the dest datatype (#85140)
The AMP inserts `_autocast_to_reduced_precision` and `_autocast_to_full_precision` automatically. The aten implementation provides a fast path to bypass the conversion if the tensor data type has been the reduced/full precision. But NNC always does the conversion which could bring >5% E2E performance regression.
This PR is to address the performance issue like aten. We will not pull `_autocast_to_reduced_precision` and `_autocast_to_full_precision` into NNC fusion group and fallback to aten to trigger its fast path if the tensor data type has been the reduced/full precision.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85140
Approved by: https://github.com/frank-wei
