fix(event_handler): sync alias and validation_alias for Pydantic 2.12+ compatibility

[leandrodamascena]

Issue number: closes #7552

Summary

This PR fixes the broken behavior when setting alias or validation_alias in Query, Header, and other param classes after Pydantic 2.12.0 update.

Changes

• Set validation_alias to alias value when only alias is provided
• Set alias to validation_alias value when only validation_alias is provided
• Updated default value of validation_alias from None to _Unset in Param, Path, Query, Header, Body, and Form classes

User experience

Please share what the user experience looks like before and after this change

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.54%. Comparing base (26f44a8) to head (4c6741a).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7901   +/-   ##
========================================
  Coverage    96.54%   96.54%           
========================================
  Files          275      275           
  Lines        13199    13209   +10     
  Branches      1002     1006    +4     
========================================
+ Hits         12743    12753   +10     
  Misses         353      353           
  Partials       103      103           

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
1.8% Duplication on New Code

See analysis details on SonarQube Cloud