[Main] Add the missing part to support 1F1B overlap for Qwen3-Next

[BestJuly]

What does this PR do ?

1F1B overlap requires backward_dw while current Qwen3-Next model GND part does not define this. Add the missing part so 1F1B can be enabled (also work well together with CUDA graph).

PR for dev branch: PR#2996

⚠️ For major changes (either in lines of code or in its impact), please make sure to first share a design doc with the team. If you're unsure what's the best way to do so, contact the @mcore-oncall.

Contribution process

flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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Pre-checks

• I want this PR in a versioned release and have added the appropriate Milestone (e.g., Core 0.8)
• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
• I have run the autoformatter.sh on my PR

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For MRs into `dev` branch

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Merging your PR

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[duncanriach]

LGTM