init rust load balancer

[xutianyi1999]

Motivation

• [Roadmap] Prefill and Decoding Disaggregation #4655
  Rust PD Load Balancer

Modifications

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
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[hnyls2002]

@xutianyi1999 Please refer to #6437