add XLML tests for DeepSeek V4 Flash

[snehalv2002]

Description

Adds XLML tests for DeepSeek V4 Flash and updates the Run_DeepSeek.md doc with V4 relevant instructions.

FIXES: b/509931363

Tests

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

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

✅ All modified and coverable lines are covered by tests.

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[parambole]

@snehalv2002 could you please update the PR title as this add test scripts and updates the user guides and not XLML tests which would be part of a different PR.