Add time info through user warning for debugging purpose

[charlesli640]

Description

Add time info through user warning for debugging

b/496201097

Tests

Trigger workflow UT

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.

[codecov]

Codecov Report

❌ Patch coverage is 98.46154% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/maxtext/trainers/pre_train/train_compile.py	98.14%	1 Missing ⚠️

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