Disable dual stream execution of input projection for Qwen3

[xyang16]

Purpose

Currently dual stream execution requires custom ops that passes the layer_name as a string. This will regress cold compile times by ~4x. So this PR temporarily revert dual stream optimization in Qwen3 and Qwen3.5 models.

TODO: Re-enable dual stream after #38123 and upgrade to Pytorch 2.11.

Test Plan

Tested with Qwen3 and Qwen3.5 models.

vllm serve Qwen/Qwen3-Next-80B-A3B-Instruct \
    --tensor-parallel-size 1 \
    --max-num-seqs 16 \
    --no-enable-prefix-caching

vllm serve Qwen/Qwen3.5-35B-A3B \
    --tensor-parallel-size 1 \
    --max-num-seqs 16 \
    --no-enable-prefix-caching

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Essential Elements of an Effective PR Description Checklist

• 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
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[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[gemini-code-assist]

Code Review

This pull request refactors the input projection logic within the Qwen3_5 and Qwen3_Next models. It removes the custom gdn_in_proj operation, its fake implementation, and the associated _forward_in_proj method that utilized maybe_execute_in_parallel. The input projection now directly calls self.in_proj_qkvz and self.in_proj_ba instead of relying on the custom operation. There are no review comments to address.

[xyang16]

cc @zou3519 @benchislett

[zou3519]

thanks, sorry for the trouble