Fix ReturnData.xr.*

[dweindl]

Fix generating xarrays in ReturnData.xr.*. Broke during renaming 'parameters'. Increase test coverage.

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.61%. Comparing base (63f2e78) to head (2ed991c).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
python/sdist/amici/sim/sundials/_numpy.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3054      +/-   ##
==========================================
- Coverage   78.16%   77.61%   -0.55%     
==========================================
  Files         313      313              
  Lines       20656    20661       +5     
  Branches     1500     1499       -1     
==========================================
- Hits        16145    16037     -108     
- Misses       4502     4615     +113     
  Partials        9        9              

Flag	Coverage Δ
cpp	71.71% <83.33%> (+0.10%)	⬆️
cpp_python	37.24% <16.66%> (-0.01%)	⬇️
petab	45.86% <16.66%> (-0.01%)	⬇️
petab_sciml	13.83% <16.66%> (+<0.01%)	⬆️
python	70.31% <83.33%> (+0.10%)	⬆️
sbmlsuite-jax	?

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Files with missing lines	Coverage Δ
python/sdist/amici/sim/sundials/_numpy.py	87.42% <83.33%> (+12.74%)	⬆️

... and 5 files with indirect coverage changes

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