helper functions for creating schemas

[samuelcolvin]

Also reordered schema definitions to make more sense.

[codecov-commenter]

Codecov Report

Merging #263 (b4c6e53) into main (df756fb) will decrease coverage by 0.05%.
The diff coverage is 99.52%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #263      +/-   ##
==========================================
- Coverage   98.60%   98.55%   -0.06%     
==========================================
  Files          51       51              
  Lines        5229     5242      +13     
  Branches       37       38       +1     
==========================================
+ Hits         5156     5166      +10     
- Misses         73       75       +2     
- Partials        0        1       +1     

Impacted Files	Coverage Δ
pydantic_core/core_schema.py	99.03% <99.52%> (-0.97%)	⬇️
src/input/input_python.rs	98.14% <0.00%> (-0.26%)	⬇️
src/validators/typed_dict.rs	99.08% <0.00%> (-0.02%)	⬇️

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