Refactor DeepLabCut CSV read and validation

[lochhh]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
Closes #716

What does this PR do?

• updates the logic to compare only the non-numeric levels in ValidDeepLabCutCSV
• stores the read column levels in the ValidDeepLabCutCSV object for use in _df_from_dlc_csv
• simplifies read_csv call (note that there is a much simpler way to do this for typical cases as mentioned in Simplify DeepLabCut CSV read #716, but this approach is one that "works-for-all"; the other alternative would be to have two pathways: use read_csv with index_col=0 if the first row is not empty, otherwise use read_csv without index_col and set/reset the MultiIndex/index names after).

References

#716

How has this PR been tested?

Existing tests passing

Is this a breaking change?

No

Does this PR require an update to the documentation?

No

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (d5544d9) to head (cfb141a).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #715   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           34        34           
  Lines         2070      2068    -2     
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- Hits          2070      2068    -2     

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[niksirbi]

Thanks @lochhh! It's nice to avoid parsing the CSV header twice. This is good-to-go!