Cylindrical and spherical versions of SurfaceFlux

[RemDelaporteMathurin]

Proposed changes

This PR implements the SurfaceFlux in cylindrical and spherical coordinates: SurfaceFluxCylindrical and SurfaceFluxSpherical as well as a little bit of refactoring.

Usage:

full_coverage_cylindrical_surface_flux = F.SurfaceFluxCylindrical(field="solute", surface=1)
half_coverage_cylindrical_surface_flux = F.SurfaceFluxCylindrical(field="solute", surface=1, azimuthal_range=(0, np,pi))

Similarly for spherical meshes:

full_coverage_spherical_surface_flux = F.SurfaceFluxSpherical(field="solute", surface=1)
quarter_coverage_spherical_surface_flux = F.SurfaceFluxSpherical(field="solute", surface=1, azimuthal_range=(0, np,pi), polar_range=(0, np.pi))

Types of changes

What types of changes does your code introduce to FESTIM?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

• Black formatted
• Unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[RemDelaporteMathurin]

@jhdark let me know what you think and I'll complete with documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.48%. Comparing base (91e59ac) to head (7d841f0).
Report is 5 commits behind head on main.

Additional details and impacted files

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+ Coverage   99.47%   99.48%   +0.01%     
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  Lines        2290     2349      +59     
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+ Hits         2278     2337      +59     
  Misses         12       12              

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[jhdark]

This looks great to me, also like the fact that the units of the results are given in the doc strings, think this is smth we could implement in other export classes (accounting for differences in different dimensions).

However, just some small coverage tests that need to be added.

Then its good to go!

[RemDelaporteMathurin]

the units of the results are given in the doc strings, think this is smth we could implement in other export classes (accounting for differences in different dimensions)

Maybe what we should do is add the units in the docstrings and also in the title of the csv column based on the dimension of the mesh

[jhdark]

I like the idea, although this could be a big change, we can add in another PR. I can make a new issue

[jhdark]

LGTM