Modify subdomain labeling strategy in CDT3 -> TetRemesh triangulation

[MaelRL]

Summary of Changes

The conversion from a CDT3 triangulation to a tetrahedral remeshing triangulation labels cells with a subdomain index that is either 0 if the cell is in the (constrained) connected component of the infinite vertex, and 1 otherwise.

But face constraints can also reflect multiple subdomains, and possibly nested subdomains, which we might want to remesh differently.

The following PR modifies the labeling during conversion such that a flood algorithm is used to mark constrained connected components.

• The connected component containing the infinite vertex is marked with index 0.
• Nested components are marked with increasing indices.
• Disconnected components that have the same nesting level get the same index parity: for example two cubes within a larger bounding box will be index 2 and 4.

TODO:

• Should there be a strategy tag? Similar to https://doc.cgal.org/latest/Polygon_repair/index.html#Chapter_2D_Polygon_repair
• This is somewhat related to CGAL::mark_domain_in_triangulation (by the way, here is a 3D version for CDT3: https://gist.github.com/MaelRL/9076cc491cd24b7a9c6f6e317263bdfe which could be part of this PR).
• Modified example: https://gist.github.com/MaelRL/d10daf116f562b87bc9fb854f5eeff23

Release Management

• Affected package(s): Constrained_triangulation_3
• Issue(s) solved (if any): -
• Feature/Small Feature (if any): WIP
• Link to compiled documentation (obligatory for small feature) wrong link name to be changed
• License and copyright ownership: no change

[lrineau]

Looks good to me, except for the use of std::list.

[lrineau]

Why std::list? That code does not need to splice or insert/remove in the middle of the container.
Use std::stack.