`rendering/quality/shadows` is now `rendering/quality/positional_shadow`
to explicitly denote that the settings only affect positional light shadows,
not directional light shadows.
Shadow atlas settings now contain the word "atlas" for easier searching.
Soft shadow quality settings were renamed to contain the word "filter".
This makes the settings appear when searching for "filter" in the
project settings dialog, like in Godot 3.x.
Initial TAA support based on the implementation in Spartan Engine.
Motion vectors are correctly generated for camera and mesh movement, but there is no support for other things like particles or skeleton deformations.