Support FP4 gemm and FP4 checkpoints

[trevor-m]

Motivation

This PR adds support for modelopt FP4 quantized models.
Tested using fp4 quantized Llama 3.1 model.

This work was adapted from the following - thanks @pavanimajety @kaixih @kushanam!
vllm-project/vllm#12784
vllm-project/vllm#13571
vllm-project/vllm#12520

Modifications

Adds two operations to sgl-kernel:

• scaled_fp4_quant - Quantize bf16 or fp16 input to fp4 and returns input scale in block interleaved format
• cutlass_scaled_fp4_mm - Perform fp4 gemm

Adds modelopt_fp4 quantization method.
Adds ModelOptFp4Config and ModelOptFp4LinearMethod to utilize new fp4 kernels for linear layers

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