Partial backport to 3.x LTS

[Firepal]

Every single shader in the main branch was modified to support Godot 4.x and use the new include macro. This obviously caused those shaders to be incompatible with 3.x.

One of these days I would like to backport these, and perhaps some GDScript stuff. As far as I'm concerned, automating this process via scripting is not really feasible, and this would have to be done by-hand.