Add OpenAPI 3.2.0 support (OAS32Validator)

[philfreo]

Summary

• Adds OAS32Validator and oas32_format_checker for OpenAPI 3.2.0 schema validation
• OAS 3.2 still uses JSON Schema Draft 2020-12 (same as 3.1), so the validator follows the same pattern as OAS31Validator
• Includes tests mirroring the existing OAS 3.1 test suite

Closes #255

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.50%. Comparing base (79a85d7) to head (d3740fb).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #256      +/-   ##
==========================================
+ Coverage   81.91%   82.50%   +0.58%     
==========================================
  Files           6        6              
  Lines         271      280       +9     
  Branches       56       56              
==========================================
+ Hits          222      231       +9     
  Misses         31       31              
  Partials       18       18              

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