feat: Enhance ai-cache Plugin with Vector Similarity-Based LLM Cache Recall and Multi-DB Support

[EnableAsync]

Ⅰ. Describe what this PR did

This PR extends the functionality of the ai-cache plugin, enabling more efficient AI application development by introducing vector similarity-based caching and recall mechanisms.

Ⅱ. Does this pull request fix one issue?

Please refer to issue #1040 and #1041.

Ⅲ. Why don't you add test cases (unit test/integration test)?

Test cases will be added later.

Ⅳ. Describe how to verify it

After filling in the apikey and ChromaCollectionID in docker-compose-test/envoy.yaml, execute the following code:

cd docker-compose-test/
docker compose up

Then test it by accessing the LLM via cURL:

curl http://172.17.0.1:10000/v1/chat/completions -X POST -d '{"model":"gpt-4o-mini","messages":[{"content":"今天中午吃什么","role":"user"}]}' -H "Content-Type: application/json"

Ⅴ. Special notes for reviews

[CLAassistant]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.52%. Comparing base (ef31e09) to head (a1a7eef).
Report is 173 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1248      +/-   ##
==========================================
+ Coverage   35.91%   43.52%   +7.61%     
==========================================
  Files          69       76       +7     
  Lines       11576    12320     +744     
==========================================
+ Hits         4157     5362    +1205     
+ Misses       7104     6622     -482     
- Partials      315      336      +21     

see 69 files with indirect coverage changes

[CH3CHO]

LGTM

[CH3CHO]

SaaS 版本的 Weaviate 似乎需要一个 API Key 才能访问。