Properly apply custom materials with CanvasGroups in the GLES3 backend
Properly blur backbuffer when using a partial rect in forward_plus and
gl_compatibility renderers
Properly set fit_margin when clear_margin is set
Fix shader error during backbuffer clear in mobile renderer
This includes collision (2D SDF, Box, Sphere, Heightmap),
attraction (Box, Sphere), and all sorting modes.
This does not include 3D SDF collisions, trails, or
manual emission.