[Nvidia] Add trtllm mnnvl allreduce

[wenscarl]

Motivation

Upstreaming the new trtllm_mnnvl_fused_allreduce_add_rmsnorm. Depends on flashinfer-ai/flashinfer#2118

This will improve throughput for multi-GPU decode for NVL systems.

Modifications

Accuracy Tests

Benchmarking and Profiling

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.

[Fridge003]

@wenscarl Is this PR ready for review?

[wenscarl]

@wenscarl Is this PR ready for review?

There is still some issue with the kernel in flashinfer.