Add Colocated Python Checkpointing

[SujeethJinesh]

Description

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the past.

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FIXES: b/123456
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Tests

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Checklist

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/common/checkpointing.py	0.00%	3 Missing and 1 partial ⚠️

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