Introspection of check constraints + .transform() supports them

[simonw]

Refs:

• Introspection methods to read check constraints #834
• .transform() drops check constraints and comments #762

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📚 Documentation preview 📚: https://sqlite-utils--835.org.readthedocs.build/en/835/

[codecov]

Codecov Report

❌ Patch coverage is 88.91455% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.87%. Comparing base (f726ea4) to head (36e36dc).

Files with missing lines	Patch %	Lines
sqlite_utils/create_table_parser.py	87.77%	45 Missing ⚠️
sqlite_utils/db.py	95.38%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #835      +/-   ##
==========================================
- Coverage   95.55%   94.87%   -0.68%     
==========================================
  Files           9       10       +1     
  Lines        3805     4238     +433     
==========================================
+ Hits         3636     4021     +385     
- Misses        169      217      +48     

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[simonw]

New documentation:

• https://sqlite-utils--835.org.readthedocs.build/en/835/python-api.html#checks
• https://sqlite-utils--835.org.readthedocs.build/en/835/python-api.html#check-constraints
• https://sqlite-utils--835.org.readthedocs.build/en/835/changelog.html#unreleased