Add Valve Index controller JSON bindings
Add contoller bindings for the Valve Index controllers (knuckles) on the ParaView side, for both OpenVR / OpenXR.
This MR go upstream coming modifications on the VR interactor style (vtkVRInteractorStyle), in order to make the controls feel more intuitive (see vtk/vtk!9157 (merged)). This explains why /actions/vtk/in/startelevation
and /actions/vtk/in/elevation
are present in the JSON files.