[Future Spherical Class] Add SPoint and SMultiPoint

[ghiggi]

This PR add the SPoint and SMultiPoint class of the future spherical geometry interface.

• [x] Tests added
• [x] Tests passed
• [x] Passes git diff origin/main **/*py | flake8 --diff

[codecov[bot]]

Codecov Report

Merging #465 (a48ac65) into main (5f53ecd) will decrease coverage by 0.03%. The diff coverage is 92.96%.

@@            Coverage Diff             @@
##             main     #465      +/-   ##
==========================================
- Coverage   94.27%   94.24%   -0.04%     
==========================================
  Files          69       73       +4     
  Lines       12394    12703     +309     
==========================================
+ Hits        11685    11972     +287     
- Misses        709      731      +22     

Flag	Coverage Δ
unittests	94.24% <92.96%> (-0.04%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pyresample/spherical.py	92.67% <80.17%> (-5.55%)	:arrow_down:
pyresample/future/spherical/__init__.py	100.00% <100.00%> (ø)
pyresample/future/spherical/point.py	100.00% <100.00%> (ø)
pyresample/test/test_sgeom/__init__.py	100.00% <100.00%> (ø)
pyresample/test/test_sgeom/test_point.py	100.00% <100.00%> (ø)
pyresample/test/test_spherical.py	100.00% <100.00%> (ø)
pyresample/_multi_proc.py	83.01% <0.00%> (+1.88%)	:arrow_up:

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[coveralls]

Coverage remained the same at 93.761% when pulling a48ac65696f7d109088e95972c96d7cd5eaff240 on ghiggi:feature-spoint into 5f53ecdfa56c3d75f79be56770f1871d38873aad on pytroll:main.

[ghiggi]

@djhoese @mraspaud this is ready for review. Tomorrow I have faculty meetings, but I can finalize the last details on Friday if you manage to review it tomorrow. This PR is required for the next SArc class PR

[ghiggi]

@mraspaud @djhoese ready for merging I guess ;)

[ghiggi]

I just added a small class method from_degrees to avoid calling np.deg2rad in many occasions when creating the object