Create vtk filter from PVCreateConstantAttributePerRegion PV plugin in geos-mesh and refactor + move PV plugin to geos-pv

In the context of the repository refactoring, this will consists in two main tasks:
    - Move the Paraview plugin to geos-pv and adapte it to use the vtk filter
    - Create a VTK filter independant of the paraview plugin in geos-mesh