STRATCONN-6300 - [Mixpanel Web] - more bugfixes

[joe-ayoub-segment]

Settings and other bug fixes for new Mixpanel web destination.

Testing

Not in use by customers yet.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 31.86%. Comparing base (354c651) to head (fcf406d).

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3512       +/-   ##
===========================================
- Coverage   80.37%   31.86%   -48.52%     
===========================================
  Files        1528       15     -1513     
  Lines       29449      747    -28702     
  Branches     6298      126     -6172     
===========================================
- Hits        23670      238    -23432     
+ Misses       4914      509     -4405     
+ Partials      865        0      -865     

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