feat: ai-proxy support custom error handler by cover util.ErrorHandler

[pepesi]

Ⅰ. Describe what this PR did

解决如 #1532 描述的问题，允许替换错误处理部分，添加自定义逻辑

Ⅱ. Does this pull request fix one issue?

#1532

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

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.52%. Comparing base (ef31e09) to head (a25be3f).
Report is 206 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1537      +/-   ##
==========================================
+ 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

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