build: use pydantic-compat library

[tlambert03]

I pulled out most of the pydantic cross-compatibility stuff that I added in #205 (along with stuff I did for useq-schema and psygnal), and make a new library: https://github.com/tlambert03/pydantic-compat

this PR uses it and pulls out most of the patch logic here

this also includes and closes #220
it also pins xmlschema in tests... see #221

[codecov]

Codecov Report

Merging #213 (3ec4e8a) into main (1b31ab1) will decrease coverage by 0.37%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #213      +/-   ##
==========================================
- Coverage   86.48%   86.11%   -0.37%     
==========================================
  Files          26       26              
  Lines        1250     1217      -33     
==========================================
- Hits         1081     1048      -33     
  Misses        169      169              

Files Changed	Coverage Δ
src/ome_autogen/_generator.py	100.00% <ø> (ø)
src/ome_autogen/main.py	100.00% <ø> (ø)
src/ome_types/_conversion.py	95.87% <100.00%> (-0.03%)	⬇️
src/ome_types/_mixins/_base_type.py	93.82% <100.00%> (-0.15%)	⬇️
src/ome_types/_mixins/_kinded.py	100.00% <100.00%> (ø)
src/ome_types/_mixins/_ome.py	97.91% <100.00%> (-0.05%)	⬇️
src/ome_types/_pydantic_compat.py	97.29% <100.00%> (-1.17%)	⬇️

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[codspeed-hq]

CodSpeed Performance Report

Merging #213 will not alter performance

_{Comparing pydantic-compat (3ec4e8a) with main (1b31ab1)}

Summary

✅ 9 untouched benchmarks