fix(ai-proxy): URL encode model name in Bedrock requests

[HecarimV]

Ⅰ. Describe what this PR did

Resolve model name encoding in Bedrock provider for ai-proxy

• URL encode model names in request body to handle special characters
• Remove redundant URL encoding function

Ⅱ. Does this pull request fix one issue?

fix: #2230

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.07%. Comparing base (ef31e09) to head (0ec2a6b).
Report is 523 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2321       +/-   ##
===========================================
+ Coverage   35.91%   46.07%   +10.16%     
===========================================
  Files          69       81       +12     
  Lines       11576    13010     +1434     
===========================================
+ Hits         4157     5995     +1838     
+ Misses       7104     6670      -434     
- Partials      315      345       +30     

see 78 files with indirect coverage changes

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[johnlanni]

LGTM