Remove old and unused project settings, update various demos for 4.2 (#1024)

- Move all demo projects that don't require Forward+/Mobile-only features
  to the Compatibility rendering method. This improves performance significantly
  on low-end devices and ensures visuals are identical to a web export
  of the demo.
- Set deadzone on all inputs to 0.2 for better gamepad usability.
- Remove reliance on `default_env.tres` to use built-in Environment
  resources in the main scene instead (which follows the preview environment
  workflow).
- Remove notices pointing to GDNative or VisualScript, since both were
  removed in 4.0.
- Various bug fixes and usability tweaks to 10+ demos.

misc/matrix_transform/README.md

@@ -8,7 +8,7 @@ For more information, see the [Matrices and Transforms](https://docs.godotengine
 
 Language: GDScript
 
-Renderer: GLES 2
+Renderer: Compatibility
 
 Check out this demo on the asset library: https://godotengine.org/asset-library/asset/584
 

misc/matrix_transform/project.godot

@@ -23,8 +23,6 @@ config/icon="res://icon.webp"
 
 [rendering]
 
+renderer/rendering_method="gl_compatibility"
+renderer/rendering_method.mobile="gl_compatibility"
 anti_aliasing/quality/msaa_3d=2
-quality/driver/driver_name="GLES2"
-vram_compression/import_etc=true
-vram_compression/import_etc2=false
-environment/default_environment="res://default_env.tres"