potential memory leak fix

[dapper91]

• python 3.13 support added.
• removed validation errors from a function frame local variables to get rid of potential memory leak. See Severe memory leak #222
• union validation error location fixed.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.06%. Comparing base (b95ef02) to head (4a594a3).

Files with missing lines	Patch %	Lines
pydantic_xml/serializers/factories/model.py	50.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #223      +/-   ##
==========================================
+ Coverage   92.05%   92.06%   +0.01%     
==========================================
  Files          29       29              
  Lines        1648     1651       +3     
==========================================
+ Hits         1517     1520       +3     
  Misses        131      131              

Flag	Coverage Δ
unittests	92.06% <94.44%> (+0.01%)	⬆️

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