feat(dispatcher/proxy-agent): new diagnostics event 'undici:proxy:connected'

[SuperOleg39]

This relates to...

#4619

Rationale

Changes

Features

Bug Fixes

Breaking Changes and Deprecations

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented
• Review ready
• In review
• Merge ready

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.88%. Comparing base (148e0ef) to head (d6a3895).
⚠️ Report is 43 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##           main    #4659       +/-   ##
=========================================
+ Coverage      0   92.88%   +92.88%     
=========================================
  Files         0      106      +106     
  Lines         0    33284    +33284     
=========================================
+ Hits          0    30915    +30915     
- Misses        0     2369     +2369     

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[mcollina]

lgtm