Duplex stt rebased

[kevinhu-nv]

What does this PR do ?

Merge duplex STT changes to NeMo main.

Collection: speechlm2

Changelog

• Added training support for using nano-9b as LLM backbone
• Added prompt tokens support
• Added streaming ASR support
• Added Refactoring, unit tests, and other minor changes

Pre checks:

• [ ] Make sure you read and followed Contributor guidelines
• [X ] Did you write any new necessary tests?
• [ X ] Did you add or update any necessary documentation?
• [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  • [ ] Reviewer: Does the PR have correct import guards for all optional libraries?

PR Type:

• [X] New Feature
• [ ] Bugfix
• [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.

Who can review?

Anyone in the community is free to review the PR once the checks have passed. Contributor guidelines contains specific people who can review PRs to various areas.

Additional Information

• Related to # (issue)