DM-53999: Improve handling and validation of column overrides

[JeremyMcCormick]

This PR improves the handling of column overrides:

• Added an _update_from_overrides method on Column for updating attributes from a ColumnOverrides object
  • Used model_fields_set in this method so that explicitly setting some attributes to None is allowed (specifically, description and tap_column_index)
  • Added a validation method to make sure that overriding certain fields to None is disallowed
• Set model_config on ColumnOverrides, copied from the default Felis config (needs to be done explicitly since ColumnOverrides does not inherit from Felis's base model class)
• Added significantly better test coverage

Checklist

• Ran Jenkins
• Added a release note for user-visible changes to docs/changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.75%. Comparing base (5e449c1) to head (d32821d).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
+ Coverage   91.58%   91.75%   +0.17%     
==========================================
  Files          13       13              
  Lines        2031     2038       +7     
  Branches      291      293       +2     
==========================================
+ Hits         1860     1870      +10     
+ Misses        111      110       -1     
+ Partials       60       58       -2     

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[timj]

I have some comments that I think need addressing.

[timj]

one comment about logging