Avoid accidental NWCSAF-GEO type promotion

[gerritholl]

Avoid accidentally promoting the type in the NWCSAF GEO reader.

WARNING: Needs pytroll/trollimage#176 !

• Closes nwcsaf-geo reader turns uint8 into int64 on numpy 2.0 #2872
• Tests added
• Fully documented

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.97%. Comparing base (c924d9d) to head (7a29463).
Report is 402 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2874   +/-   ##
=======================================
  Coverage   95.97%   95.97%           
=======================================
  Files         368      368           
  Lines       53973    53982    +9     
=======================================
+ Hits        51801    51810    +9     
  Misses       2172     2172           

Flag	Coverage Δ
behaviourtests	4.02% <0.00%> (-0.01%)	⬇️
unittests	96.07% <100.00%> (+<0.01%)	⬆️

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[gerritholl]

Oops 1: with this pull request, loading and computing cloudtype fails with ValueError on numpy 2.0.

Oops 2: this appears to be not caught by any tests.

[djhoese]

Oops

Nevermind then, I don't approve 😉

[coveralls]

Pull Request Test Coverage Report for Build 10269258953

Details

• 12 of 12 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 96.073%

---

Totals
Change from base Build 10259110188:	0.0%
Covered Lines:	52039
Relevant Lines:	54166

---

💛 - Coveralls

[gerritholl]

The ValueError is due to a numpy2-incompatibility in trollimage:

https://github.com/pytroll/trollimage/blob/main/trollimage/colormap.py#L182

outside_range_bin = max(np.nanmax(arr), values.max()) + 1

numpy 1.24: uint8(255) + 1 == int64(256)

numpy 2.0: uint8(255) + 1 = uint8(0)

[gerritholl]

Oops

Nevermind then, I don't approve 😉

Fixed with pytroll/trollimage#176.