Fixed issue in irregular regridding regarding scalar coordinates

[schlunma]

Description

#1811 introduced the addition of scalar coordinate to the output of the irregular regridding. However, by mistake, I read the scalar coordinates from the source representant, not the source cube itself. Since the representant is the result of slicing the source, it potentially contains many (unwanted) scalar coordinates and also leads to the bug described in #1844.

This PR fixes that.

Closes #1844

Link to documentation:

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[codecov]

Codecov Report

Merging #1845 (80cdf5d) into main (5107f12) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1845   +/-   ##
=======================================
  Coverage   91.54%   91.54%           
=======================================
  Files         203      203           
  Lines       10945    10945           
=======================================
  Hits        10020    10020           
  Misses        925      925           

Impacted Files	Coverage Δ
esmvalcore/preprocessor/_regrid_esmpy.py	89.88% <100.00%> (ø)

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[schlunma]

Hi @LisaBock, I think this should fix your bug, could you please try your recipe with this change? Sorry for messing this up in the first place in #1811!

[LisaBock]

My recipes test was successfull.
Thanks @schlunma for the quick fix!

[remi-kazeroni]

LGTM, thanks @schlunma and @LisaBock!

[valeriupredoi]

cheers for this, you three (not an Xmas reference, I promise 🎄 ) - @remi-kazeroni since Lisa approved as well, feel free to merge 👍