[Dev] Layer/RMS Norm + Quantization Fusion

[yaox12]

What does this PR do ?

PR to the main branch: #2406

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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• I have added relevant unit tests
• I have added relevant functional tests
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[yaox12]

Close this PR in favor of #3039.