Fix hyphen parser with default

[sfc-gh-tdwojak]

What does this PR do?

Fixing: #731
Using dashes (or hyphens) is sometimes more common and jsonargparse supports this (see #301). However, when resolving default values for arguments in a nested dataclass, it does not normalize arguments with underscores, which results in NSKeyError (see the issue).

This PR adds the normalization line dest = dest.replace("-", "_") that resolves the problem.

Before submitting

• Did you read the contributing guideline?
• [] Did you update the documentation? (readme and public docstrings)
• Did you write unit tests such that there is 100% coverage on related code? (required for bug fixes and new features)
• Did you verify that new and existing tests pass locally?
• Did you make sure that all changes preserve backward compatibility?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6ad1dd6) to head (0c71303).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #736   +/-   ##
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  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines         6857      6858    +1     
=========================================
+ Hits          6857      6858    +1     

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[mauvilsa]

Looks good!