Refactored shadowmapping.

- Made shadow bias size independent, so it will remain when changing light or camera size.
- Implemented normal offset bias, which greatly enhances quality.
- Added transmission to subsurface scattering
- Reimplemented shadow filter modes

Closes #17260

editor/plugins/node_3d_editor_plugin.h

@@ -218,6 +218,7 @@ class Node3DEditorViewport : public Control {
 		VIEW_DISPLAY_DEBUG_SCENE_LUMINANCE,
 		VIEW_DISPLAY_DEBUG_SSAO,
 		VIEW_DISPLAY_DEBUG_ROUGHNESS_LIMITER,
+		VIEW_DISPLAY_DEBUG_PSSM_SPLITS,
 		VIEW_LOCK_ROTATION,
 		VIEW_CINEMATIC_PREVIEW,
 		VIEW_AUTO_ORTHOGONAL,