Add vtkContourTriangulator to vtkDelaunay2D documentation

VTK users may not be aware that the contour tringulator is often a superior replacement for 2D Delaunay.

See https://discourse.vtk.org/t/constrained-vtkdelaunay2d-failure-with-3-holes-bug-use-vtkcontourtriangulator-instead/14834/5

requested review from @dgobbi

Warnings:

• please consider adding a changelog entry in a file ending with .md in Documentation/release/dev.

The warnings do not need to be fixed, but it is recommended to do so.

+2

do: merge

mentioned in commit 95b50bc4

merged manually

mentioned in commit jean.fechter/paraview@eb304b69

mentioned in commit jean.fechter/paraview@bf0488e2

mentioned in commit thomas.galland/paraview@c820fe1e

mentioned in commit thomas.galland/paraview@24d26723

mentioned in commit thomas.galland/paraview@f9171e9d

mentioned in commit thomas.galland/paraview@ef9f024b

mentioned in commit jean.fechter/paraview@6a5d3037

mentioned in merge request paraview/paraview!7107 (merged)

mentioned in commit thomas.galland/paraview@d944ad0b