[Cherry-Pick][RL] Adapt async rollout checkpoint update flow(#7042)

[jackyYang6]

Motivation

This PR cherry-picks #7042 to release/2.5.

It aligns the async rollout checkpoint update flow with develop, including the update_weights parameter update from rsync_config to verify_checksum, and keeps the route validation test in sync.

💡 If this PR is a Cherry Pick, the PR title needs to follow the format by adding the [Cherry-Pick] label at the very beginning and appending the original PR ID at the end. For example, [Cherry-Pick][CI] Add check trigger and logic(#5191)

💡 如若此PR是Cherry Pick，PR标题需遵循格式，在最开始加上[Cherry-Pick]标签，以及最后面加上原PR ID，例如[Cherry-Pick][CI] Add check trigger and logic(#5191)

Modifications

• Align update_weights parameter passing in the RL async update flow
• Adapt checkpoint verification parameter propagation across:
  • api_server
  • gpu_worker
  • gpu_model_runner
  • dynamic_weight_manager
• Sync the same control-path adaptation for Metax worker/model runner
• Fix cross-layer interface mismatch in async rollout checkpoint updates

Usage or Command

Example control request used in RL async integration:

curl http://<host>:<port>/v1/update_weights \
  -H "Content-Type: application/json" \
  -d '{
    "version": "0",
    "verify_checksum": false
  }'

Typical control flow during async rollout:

pause -> update_weights -> resume

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]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 28.00000% with 18 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/2.5@971fc7c). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/rl/dynamic_weight_manager.py	6.25%	15 Missing ⚠️
fastdeploy/entrypoints/openai/api_server.py	66.66%	0 Missing and 1 partial ⚠️
fastdeploy/worker/gpu_model_runner.py	66.66%	1 Missing ⚠️
fastdeploy/worker/gpu_worker.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             release/2.5    #7084   +/-   ##
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  Coverage               ?   69.03%           
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  Files                  ?      390           
  Lines                  ?    54077           
  Branches               ?     8515           
==============================================
  Hits                   ?    37334           
  Misses                 ?    14039           
  Partials               ?     2704           

Flag	Coverage Δ
GPU	69.03% <28.00%> (?)

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