Layer/RMS Norm + Quantization Fusion

[yaox12]

What does this PR do ?

Ideally, we should use LayerNormLinear to fuse normalization and quantization. But there're some exceptions, e.g., in MLA, we're using separate input layernorm and Linear layers. So we provide this option to fuse quantization in LayerNorm/RMSNorm.

Another option is to use a single GEMM for both kv_down/q_down projection in MLA, just like what we're doing for GQA/MHA, so we can do the fusion through TE's LayernormLinear. We will wait for the final decision.

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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[yaox12]

These args were once removed but re-added in 67a0e5d. I thought it was by accident.

[yaox12]

Close this PR in favor of #3039.