Update gmm2 fork

[shuningjin]

Description

1. Refork tokamax gmm2, source file. remote changes since initial fork

2. Re-apply local changes in maxtext gmm2 since initial fork (local changes).

diff between source file and this PR: diff

Tests

N/A

Checklist

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• I have performed a self-review of my code. For an optional AI review, add the gemini-review label.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have run end-to-end tests tests and provided workload links above if applicable.
• I have made or will make corresponding changes to the doc if needed, including adding new documentation pages to the relevant Table of Contents (toctree directive) as explained in our documentation.