[BugFix] [RL] remove shutdown_process_group/restart_process_group for RL

[liyonghua0910]

Motivation

之前有个 PR (#5249) 让 FD 在 clear weight 之后回到 worker 的主循环，而未考虑到 clear weight 时也关闭了通信组，导致 worker 主循环中的通信操作失败。

解决方式：清理权重时不再关闭通信组，更新权重时也不需要再重建

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Modifications

Usage or Command

Accuracy Tests

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
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• Add unit tests. Please write the reason in this PR if no unit tests.
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[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@33e4f88). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/worker/worker_process.py	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #5433   +/-   ##
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  Coverage           ?   59.53%           
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  Files              ?      327           
  Lines              ?    40634           
  Branches           ?     6168           
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  Hits               ?    24193           
  Misses             ?    14576           
  Partials           ?     1865           

Flag	Coverage Δ
GPU	59.53% <0.00%> (?)

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