feat: implements healpix geometry

[faouziH21]

Closes #2329

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 121 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.97%. Comparing base (c1a2993) to head (20c98b2).
⚠️ Report is 540 commits behind head on main.

Files with missing lines	Patch %	Lines
src/t8_cmesh/t8_cmesh_healpix/t8_cmesh_healpix.cxx	0.00%	79 Missing ⚠️
.../t8_cmesh/t8_cmesh_healpix/t8_geometry_healpix.cxx	0.00%	28 Missing ⚠️
.../t8_cmesh/t8_cmesh_healpix/t8_geometry_healpix.hxx	0.00%	14 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2327      +/-   ##
==========================================
+ Coverage   78.45%   81.97%   +3.52%     
==========================================
  Files         115      119       +4     
  Lines       19184    18689     -495     
==========================================
+ Hits        15050    15320     +270     
+ Misses       4134     3369     -765     

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[Davknapp]

Thanks for the addition! Please address my comments. I am looking forward to merge it!

[Davknapp]

Please use our indentation script to fix the indentation. Also have a look at the output of the doxygen check to see which functions need documentation.

[Davknapp]

Please document the struct