New option -fem replacing -nofem

[corentin-prigent]

This update removes the option -nofem and adds a new option -fem which takes an integer as a parameter:

• -fem 0 mimics the exact behaviour of -nofem.
• -fem 1 is the default behaviour: mmg forces the output mesh to be finite element compatible.
• -fem 2 adds the option to also prevent the creation of regular boundary edges linking two features points (ridges or non-manifold). This stems from PR Force the split of regular boundary edges connecting ridge or non-manifold vertices #229.

mmg2d source code has been modified only in order to match the new options of mmg3d. No new features have been added to mmg2d.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.29%. Comparing base (4e2f535) to head (2ba54f5).
⚠️ Report is 33 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #298      +/-   ##
===========================================
- Coverage    50.31%   50.29%   -0.03%     
===========================================
  Files          177      177              
  Lines        47881    47852      -29     
  Branches     10362    10358       -4     
===========================================
- Hits         24093    24067      -26     
- Misses       16047    16051       +4     
+ Partials      7741     7734       -7     

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[taupalosaurus]

Also, can you please update the comments documenting info.setfem and info.fem in libmmgtypes.h

[taupalosaurus]

And add a test for option setfem=2