[Small Feature] Region Growing Revision

[danston]

This PR is a revision of the Region_growing component from the Shape_detection package. It includes multiple small and big changes (including a few breaking changes!):

• added named parameters (that changed the APIs of many class constructors)
• now the update function from the RegionType concept returns a boolean flag that enables to detect if the input conditions for the new region are satisfied (it is also a breaking change)
• old fitting classes are now using better versions of the region conditions, more precise and faster, including the correct normal orientations
• added new classes for getting linear regions in a set of 2D and 3D segments
• added the Polyline_graph class for extracting a set of polylines from a face graph, which splits this graph into a set of user-defined regions (this is necessary for the decimation algorithm in the PMP)
• added new classes for getting linear regions on 2D and 3D polylines
• added several internal functions, which are not yet public, since I am not sure whether we really want to document them
• extended docs with new examples
• better and stricter tests for the test suite
• a few other fixes and internal changes
• fixed the Polyhedron demo using new API

To be yet done:

• this version should be later merged with the PR [Small Feature] Region Growing on Spheres and Cylinders #5808 that extends the region growing algorithm with detecting circles, spheres, and cylinders

The doc files changed:

• the concept RegionType.h
• Shape_detection.txt (sections Segment Set, Polyline, Deprecated)
• named parameters descriptions for all headers in the ref manual for Region Growing
• Segment Set and Polyline classes

TODO:

• shall Polygon_mesh sub-namespace/headers be renamed Triangle_mesh? is not a good name
• Region growing using planes on mesh is not using a property map (example is not generic at all)
• Remove Item_to_region_index_map?
• Replace DOXYGEN_NS by DOXYGEN_RUNNING?
• Clean and properly document CGAL/Shape_detection/Region_growing/internal/free_functions.h

Release Management

• Affected package(s): Shape_detection
• Issue(s) solved (if any): no issues
• Feature/Small Feature (if any): Small Feature
• Link to compiled documentation (obligatory for small feature): docs
• License and copyright ownership: Inria and GF

Tasks:

• Remove tmp modif in the docs

[sloriot]

Replaced by #6702