[Feature] Support report token index by attention store

[rainyfly]

Motivation

1. AttentionStore支持上报token。

Modifications

新增接口 flush_token_index

Usage or Command

None

Accuracy Tests

None

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 7.40741% with 25 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@6c685c9). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/cache_manager/cache_transfer_manager.py	0.00%	12 Missing ⚠️
...transfer_factory/mooncake_store/attention_store.py	18.18%	9 Missing ⚠️
fastdeploy/cache_manager/prefix_cache_manager.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #6285   +/-   ##
==========================================
  Coverage           ?   66.66%           
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  Files              ?      385           
  Lines              ?    51284           
  Branches           ?     7998           
==========================================
  Hits               ?    34187           
  Misses             ?    14612           
  Partials           ?     2485           

Flag	Coverage Δ
GPU	66.66% <7.40%> (?)

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