Add chunk_causal_conv1d_opt_kernel in GDN for Qwen3.5

[YangQun1]

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• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

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Purpose

Add an optimized chunk causal conv1d kernel in GDN module for Qwen3.5

Test Plan

Unit test + model e2e test + performance benchmark

Test Result

Unit test

• pass

Model e2e test

• TODO

Performance benchmark

• bs=1, total token 4k config:
  • original kernel: 672 us, 20% of GDN total time
  • new kernel: 475 us, 15% of GDN total time
• bs=4, total token 16k config:
  • origin kernel: 2823 us, 25% of GDN total time
  • new kernel: 1834 us, 17% of GDN total time

(Optional) Documentation Update

BEFORE SUBMITTING, PLEASE READ https://docs.vllm.ai/en/latest/contributing (anything written below this line will be removed by GitHub Actions)