feat: column selectors for defining columns in validation workflow

[rich-iannone]

This PR focuses on enhancing the col_vals_* validation methods to accept Column objects, which allows for more dynamic and flexible column comparisons.

Updated the col_vals_gt(), col_vals_lt(), col_vals_eq(), col_vals_ne(), col_vals_ge(), col_vals_le(), col_vals_between(), etc., etc., validation methods to accept Column objects (through col()) in columns= argument. This includes changes to parameter documentation and the addition of logic to handle Column objects appropriately. This is lazy, in that resolution of the columns by column selectors isn't performed until the interrogate() method is called.

Also added the eval_error attribute to the _ValidationInfo class to track evaluation errors (e.g., column selectors not resolving to any columns. This provides useful information and also affects the final display of the validation report table.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.74%. Comparing base (9fd0839) to head (621f83c).
Report is 27 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #18      +/-   ##
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+ Coverage   99.73%   99.74%   +0.01%     
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  Files          11       11              
  Lines        1902     1980      +78     
==========================================
+ Hits         1897     1975      +78     
  Misses          5        5              

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