BUG: Fix linux events, keys and mouse
Key events weren't working in iMSTK since the move to manually calling VTK process events on the interactor.
Turns out there is a bug in VTK 9.0 vtkXRenderWindowInteractor::ProcessEvents which prevents it from working. vtk/vtk!6687 (merged)
This MR introduces the VTK fixes in iMSTK, we can use these until we update to VTK 10, whenever that releases.
Edited by Andrew Wilson