[ROCm] BFloat16 support (#10465)
* bf16 support
* minor clean up
* UTs
* fix build
* UTs
* UTs
* merge commit 6b5504c
* minor
* ROCm code cleanup
* fix build
* fix build
* minor
Co-authored-by: Ethan Tao <ettao@microsoft.com@orttrainingdev7.d32nl1ml4oruzj4qz3bqlggovf.px.internal.cloudapp.net>
Co-authored-by: root <root@GCRAMDRR1-MI100-087.redmond.corp.microsoft.com>
