Expose GEOSConstrainedDelaunayTriangulation as ST_TriangulatePolygon

[mdavis]

GEOS 3.11 has added ​GEOSConstrainedDelaunayTriangulation to provide Constrained Delaunay Triangulation for polygonal geometry.

How should this be exposed? Existing functions which are similar are both backed by SFGCAL: ​ST_Tesselate and ​ST_ConstrainedDelaunayTriangles. However, both of these have some additional functionality which isn't in GEOSConstrainedDelaunayTriangulation, and both produce TINs only as output. Design options include:

• add a new new function for the GEOS functionality. Perhaps ST_Triangulate or ST_TriangulatePolygon. This could output either a Polygon collection or a TIN or both (see switch on ​ST_DelaunayTriangles).
• add a branch to ST_Tesselate to use GEOS for polygonal inputs. This would be moved to be under Geometry Processing in the doc. But would be nice to allow Polygon collection output, which means adding a flag.

[mdavis]

My preference is for a new function ST_Triangulate. That indicates exactly what is computed. ST_Tesselate is less precise (the name is just inherited from SFCGAL, I believe). A net new function avoids any conflict or confusion with the CGAL functions.

[robe]

I'm fine with ST_Triangulate as a name.

[robe]

I think we settled on ST_TriangulatePolygon - ​https://postgis.net/docs//manual-3.3/ST_TriangulatePolygon.html