[PyTorch] Move FusedAdam/FusedSGD and necessary kernels from Apex to TE

[yaox12]

Description

This PR moves FusedAdam/FusedSGD and necessary multi_tensor_* kernels from Apex to TE, as well as the tests.

Type of change

• Documentation change (change only to the documentation, either a fix or a new content)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Changes

Please list the changes introduced in this PR:

• Move multi_tensor_* kernels
• Move FusedAdam
• Move FusedSGD
• Move tests

Checklist:

• I have read and followed the contributing guidelines
• The functionality is complete
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[timmoon10]

/te-ci pytorch

[timmoon10]

/te-ci pytorch

[yaox12]

@timmoon10 Can I get this PR merged if it looks good to you? It's sufficient to be a drop-in replacement of Apex.FusedAdam in MCore. Other features to be migrated or implemented will come in separate PRs.

[timmoon10]

LGTM, I confirm this is mostly copy-pasted from Apex with some minor formatting changes.