Move setuptools to setup_requires

[avalentino]

Apparently setuptools is not required at runtime

• Closes #xxxx
• Tests added
• Tests passed
• Fully documented

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.98%. Comparing base (c4ce8ee) to head (85840cf).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #624      +/-   ##
==========================================
+ Coverage   93.97%   93.98%   +0.01%     
==========================================
  Files          86       86              
  Lines       13848    13848              
==========================================
+ Hits        13013    13015       +2     
+ Misses        835      833       -2     

Flag	Coverage Δ
unittests	93.98% <ø> (+0.01%)	⬆️

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[djhoese]

I was pretty sure we used setuptools somewhere inside pyresample, but it looks like that is all done through importlib now so I think this is fine.

[djhoese]

...and I should have said: thanks.

[coveralls]

coverage: 93.686%. remained the same
when pulling 85840cf on avalentino:bugfix/setup_requires
into 9becb0d on pytroll:main.