Add fast route for operations with non-SI units

[danielhuppmann]

Please confirm that this PR has done the following:

• Tests Added
• Documentation Added
• Name of contributors Added to AUTHORS.rst
• Description in RELEASE_NOTES.md Added

Description of PR

This PR enables binary operations with non-SI units without having to explicitly use the ignore_units argument.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.8%. Comparing base (ca1bc4c) to head (3c49624).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #907   +/-   ##
=====================================
  Coverage   94.8%   94.8%           
=====================================
  Files         67      67           
  Lines       6355    6410   +55     
=====================================
+ Hits        6025    6080   +55     
  Misses       330     330           

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[phackstock]

There's a number of refactorings that I'd suggest for _op_data but I guess that is well beyond the scope of this PR.
I've left some comments below for making the tests a little bit easier to read and understand and one small refactoring suggestion for _op_data.
Since none of those affect the functionality of the PR, I'd say it's good to merge either way.

[phackstock]

Thanks for the changes @danielhuppmann, good to be merged from my side.