[Gated Delta Net] Add pallas training kernel to repo

[Rohan-Bierneni]

Description

If the change fixes a bug or a Github issue, please include a link, e.g.,:
FIXES: b/123456

Tests

Checklist

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• I have necessary comments in my code, particularly in hard-to-understand areas.
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[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 20 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...xt/kernels/attention/gated_delta_rule_attention.py	93.69%	12 Missing and 8 partials ⚠️

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