Support pickleability of classes with callable args

[euxhenh]

What does this PR do?

• adapt_class_type: Replaced the locally defined partial_instance wrapper function with a functools.partial call to construct class instantiators, ensuring they are compatible with pickle and other serialization libraries.

See discussion in #727 for more context.

Before submitting

• Did you read the contributing guideline?
• [n/a] 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)

[mauvilsa]

Thank you, looks good! Just do a small fix in the changelog.

[euxhenh]

@mauvilsa Thank you! I updated the changelog.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (b111f10) to head (88e454c).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #728   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines         6859      6857    -2     
=========================================
- Hits          6859      6857    -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.