feat: Benchmark mm_fp4 mxfp4 support and gemm autotune support. Restore mm_fp4 API behavior

[bkryu]

📌 Description

Current PR:

• flashinfer_benchmark.py enhancements:
  • Adds --autotune support for mm_fp4 and bmm_fp8 benchmarking (trtllm and cutlass backends)
  • Adds mxfp4 support for mm_fp4 benchmarking.
• Restores mm_fp4's default behavior that was changed in PR1688:
  • The use_nvfp4 input argument was added in PR1688 and set to False by default. The mm_fp4 behavior prior to PR1688 is always using nvfp4, which led to breaking existing mm_fp4 usages. Current PR sets the default True.

🔍 Related Issues

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Reviewer Notes

[nvmbreughe]

LGTM!