Move time dimension to the front in select_and_process_variables method

[rbeucher]

fix #221

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.23%. Comparing base (7549b46) to head (6f3cb08).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #230      +/-   ##
==========================================
+ Coverage   47.47%   49.23%   +1.75%     
==========================================
  Files          22       22              
  Lines        4183     4241      +58     
==========================================
+ Hits         1986     2088     +102     
+ Misses       2197     2153      -44     

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[rbeucher]

@rhaegar325, I think that is a rather small change, I am going to merge. Let me know if you get any issues