[Tracker] Porting to 4.0 and improving for 4.0

[clayjohn]

This tracker is for changes that need to be made for the TPS demo to be fully "ported" to Godot 4.0. It includes bugs that are present in the 4.0-dev branch and features we would like to see included in the full release of the demo.

Bugs

(Most reported by Calinou here)

• [x] The flying forklift doesn't move in the air, while it's supposed to circle the area.
• [x] The crosshair when aiming isn't correctly scaled (check TextureRect scale mode property).
• [ ] Some level UVs appear broken due to LOD generation, though it's not too noticeable in most areas.
• [x] Key inputs in the input map should use physical key inputs, to allow for WASD controls to work out of the box on non-QWERTY keyboard layouts. This was done in the 3.x version.
• [x] The stretch mode project setting should be changed to canvas_items (equivalent to 2d in 3.x).
• [x] Enemy aim is off

Enhancements

• [x] GI Source: Lightmaps + ReflectionProbes (fast); static VoxelGI (medium); SDFGI + SSIL (high quality)
• [x] Occlusion Culling

[clayjohn]

I have made most of the above changes in a WIP local commit. Will make a PR tomorrow