Tetrahedral remeshing - add edge flips on surfaces

[janetournois]

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[sloriot]

@janetournois this PR is marked for 5.5, are you planning to finish it before the release or shall we postpone it?

[janetournois]

let's postpone it, it will not be ready before the release

[sloriot]

Same question as for 5.5, shall we postpone it to 5.7?

[janetournois]

yes? I postponed it

[janetournois]

At this state, here are the results of the example mesh_and_remesh_polyhedral_domain_with_features.cpp

Before remeshing :

After remeshing, with flips on surfaces :

[janetournois]

This PR is ready to be tested

[sloriot]

Successfully tested in CGAL-6.0-Ic-176