feat: support for mcore optimizer (to enable MoE)

[terrykong]

What does this PR do ?

• Finishes up support for mcore optimizer
• adds tests for mixtral EP and mixtral TP + SP + peft

Rebase stack

• feat: DPO support for global padding of seq_len to a multiple #386
• feat: adds helper script for running & summarizing functional tests #387
• chore: adds missing license header on tests and corrects file modes #388
• feat: support for mcore optimizer (to enable MoE) #380

Changelog

• Please update the CHANGELOG.md under next version with high level changes in this PR.

Usage

• You can potentially add a usage example below

# Add a code snippet demonstrating how to use this 

Before your PR is "Ready for review"

Pre checks:

• Make sure you read and followed Contributor guidelines
• Did you write any new necessary tests?
• Did you add or update any necessary documentation? Make sure to also update the NeMo Framework User Guide which contains the tutorials

Checklist when contributing a new algorithm

• Does the trainer resume and restore model state all states?
• Does the trainer support all parallelism techniques(PP, TP, DP)?
• Does the trainer support max_steps=-1 and validation?
• Does the trainer only call APIs defined in alignable_interface.py?
• Does the trainer have proper logging?

Additional Information

• Related to # (issue)

[terrykong]

The DPO dataset changes should stand on their own, but are needed to test the mcore opt changes for moe. If moe issues take too long to resolve, I'll break this up.