Fix DayNightCompositor compatibility with numpy 2

[djhoese]

Requires pytroll/pyorbital#155 to be fully fixed as far as the DayNightCompositor goes. I mentioned it on slack, but basically np.some_func(float) with numpy 2 will always produce a numpy.float64. Any future calculations with that result will then upcast/promote to numpy.float64 even if there are 32-bit float arrays.

• Closes #xxxx
• Tests added
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.94%. Comparing base (816426e) to head (9339a7f).
Report is 341 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2835      +/-   ##
==========================================
+ Coverage   95.77%   95.94%   +0.16%     
==========================================
  Files         366      366              
  Lines       53501    53543      +42     
==========================================
+ Hits        51243    51371     +128     
+ Misses       2258     2172      -86     

Flag	Coverage Δ
behaviourtests	4.04% <0.00%> (+<0.01%)	⬆️
unittests	96.04% <100.00%> (+0.16%)	⬆️

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