Fix angle generation caching occassionally swapping results

[djhoese]

This PR fixes angle generation caching in the rare case that glob (which is defined as not being sorted) would return the list of zarr directories in the wrong order. My caching code assumed that it was getting the zarr files in the same order as the return results of the function being cached. And even though I know that glob behaves this way I somehow missed the sorted on the call. 🤷‍♂️

• Closes AHI HSD true_color incorrect with cache_sensor_angles  #2010
• Tests added

[djhoese]

Note in the stacked area definition test case I "moved" the area definitions over in the X dimension because them being centered on the reference longitude of the projection made them not fail my new reversed glob tests.

[codecov]

Codecov Report

Merging #2013 (92c6e29) into main (94fc4f7) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2013   +/-   ##
=======================================
  Coverage   93.55%   93.55%           
=======================================
  Files         282      282           
  Lines       41538    41548   +10     
=======================================
+ Hits        38860    38870   +10     
  Misses       2678     2678           

Flag	Coverage Δ
behaviourtests	4.77% <0.00%> (-0.01%)	⬇️
unittests	94.08% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
satpy/modifiers/angles.py	96.68% <100.00%> (ø)
satpy/tests/test_modifiers.py	100.00% <100.00%> (ø)

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[coveralls]

Coverage increased (+0.001%) to 94.013% when pulling 92c6e29 on djhoese:bugfix-angle-caching-zarr-order into 94fc4f7 on pytroll:main.

[mraspaud]

LGTM! great 🕵️ work!