[Feat] long_seq_optim

[LookAround0301]

Purpose

Test Plan

Test Result

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[gemini-code-assist]

Code Review

This pull request introduces context parallelism and sequence parallelism, which is a significant feature for handling long sequences. The changes are spread across configuration, parallel state management, and the scheduler, and appear to be logically consistent. My main feedback is to remove a temporary debug logging statement that was likely used during development.

[github-actions]

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[hmellor]

@LookAround0301 you might want to check out #23734 which seems like it might merge first

[youkaichao]

this pr is not complete.