Set lazy_load_tensors to true by default.

[niting]

Description

Lazy loading tensors saves on disk space and the path has now been optimized to be quicker with caching. Added appropriate documentation to indicate that this does not work for models with multimodal capabilities.

Tests

Ran checkpoint conversion test.

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.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!