PR #3266: Move pyconfig&pyconfig_deprecated to maxtext/configs

[hengtaoguo]

PR #3266: Move pyconfig&pyconfig_deprecated to maxtext/configs

Imported from GitHub PR #3266

Description

Move pyconfig.py and pyconfig_deprecated.py to under src/maxtext/configs.

Tests

CI

Checklist

Before submitting this PR, please make sure (put X in square brackets):

• 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.

Copybara import of the project:

--
fd028e0 by hengtaoguo hengtaoguo@google.com:

update

Merging this change closes #3266

FUTURE_COPYBARA_INTEGRATE_REVIEW=#3266 from AI-Hypercomputer:hengtaoguo-pyconfig fd028e0