The llm request can customize topk search parameters

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[codecov]

Codecov Report

Merging #217 (2102906) into dev (112aae9) will increase coverage by 0.09%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #217      +/-   ##
==========================================
+ Coverage   92.55%   92.64%   +0.09%     
==========================================
  Files          47       48       +1     
  Lines        1504     1510       +6     
==========================================
+ Hits         1392     1399       +7     
+ Misses        112      111       -1     

Impacted Files	Coverage Δ
gptcache/adapter/adapter.py	98.11% <ø> (ø)
gptcache/manager/data_manager.py	88.80% <100.00%> (+0.18%)	⬆️
gptcache/manager/vector_data/faiss.py	100.00% <100.00%> (ø)

... and 6 files with indirect coverage changes