Open requested to merge cory.quammen/vtk:opengl-projectedtetrahedra-mapper-fix into master
Fix depth buffer copy when a floating point framebuffer is available. When the bit depth of VTK's render FBO and the one used by this mapper are not the same, direct blitting from one FBO to the other does not work. Fix that by separating the color buffer blit from the depth buffer blit.
Addresses paraview/paraview#21544 and possibly paraview/paraview#19849.