feat: generate a dictionary of schema matching information when interrogating a col_schema_match() validation step

[rich-iannone]

This PR adds a method to generate schema validation info. This is added to the new val_info attr of a ValidationInfo element, providing a lot of information on what schema comparisons.

Fixes: #38

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.38%. Comparing base (e95b7f3) to head (d1ed88a).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
+ Coverage   99.36%   99.38%   +0.02%     
==========================================
  Files          12       12              
  Lines        2518     2609      +91     
==========================================
+ Hits         2502     2593      +91     
  Misses         16       16              

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