Support MLA Context Parallel (CP) exchanging latent KV

[yuzhongw-nvidia]

Description

Support MLA CP exchanging latent KV (instead of the complete KV) for ring attention.

Fixes # (issue)

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)
• [ ] Infra/Build change
• [ ] Code refactoring

Changes

Please list the changes introduced in this PR:

• Change A
• Change B

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

[nvMelissa]

Hi @yuzhongw-nvidia , thanks for your contribution! It looks like one or more of your commits aren’t signed with a Developer Certificate of Origin (DCO) , type of change, and checklist are not marked. Could you please sign your commits and update the PR? Thank you!