ENH: Update extension metadata

Consolidate extension metadata based on the corresponding s4ext file organized in the ExtensionsIndex repository.

Update scmurl, iconurl and screenshoturls to reference to the renamed repository (vtk-cgal/SlicerVESPA -> vtk/meshing/SlicerVESPA)

Update description to list the provided features along with licensing caveats.

Related:

• https://github.com/Slicer/ExtensionsIndex/pull/1925
• https://github.com/Slicer/ExtensionsIndex/issues/2041