Allow using IDAKLU(output_variables=...) with Experiments

[pipliggins]

Description

Allows users to use the output_variables option with the IDAKLU solver within an experiment.

Fixes #4386

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• [x] New feature (non-breaking change which adds functionality)
• [ ] Optimization (back-end change that speeds up the code)
• [ ] Bug fix (non-breaking change which fixes an issue)

Key checklist:

• [ ] No style issues: $ pre-commit run (or $ nox -s pre-commit) (see CONTRIBUTING.md for how to set this up to run automatically when committing locally, in just two lines of code)
• [ ] All tests pass: $ python run-tests.py --all (or $ nox -s tests)
• [ ] The documentation builds: $ python run-tests.py --doctest (or $ nox -s doctests)

You can run integration tests, unit tests, and doctests together at once, using $ python run-tests.py --quick (or $ nox -s quick).

Further checks:

• [ ] Code is commented, particularly in hard-to-understand areas
• [ ] Tests added that prove fix is effective or that feature works

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.42%. Comparing base (9560875) to head (a5f0847). Report is 202 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #4534   +/-   ##
========================================
  Coverage    99.42%   99.42%           
========================================
  Files          299      299           
  Lines        22716    22736   +20     
========================================
+ Hits         22585    22605   +20     
  Misses         131      131           

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