Improve several demos' configuration

- Enable anisotropic filtering in 3D demos, and set the quality to
  16× on desktop and 4× on mobile.
- Enable 4× MSAA on some 3D demos that didn't use it beforehand.
- On GLES3 demos, disable MSAA on mobile as these demos are often
  more demanding.
- Use more conservative framebuffer allocation settings for better
  performance.
- Use PCF13 shadow filtering in GLES2 demos on desktop to benefit
  from soft shadows in Godot 3.2.4 and later.
  In Godot 3.2.3, this will make shadows smoother but still "blocky".
- Use Lossless compression instead of VRAM compression for
  small textures such as the voxel demo texture atlas.

viewport/dynamic_split_screen/project.godot

@@ -89,5 +89,7 @@ move_right_player2={
 [rendering]
 
 quality/driver/driver_name="GLES2"
+quality/intended_usage/framebuffer_allocation=3
+quality/shadows/filter_mode=2
 environment/default_clear_color=Color( 1, 1, 1, 1 )
 environment/default_environment="res://default_env.tres"

viewport/dynamic_split_screen/split_screen.tscn

@@ -189,6 +189,8 @@ __meta__ = {
 
 [node name="Viewport1" type="Viewport" parent="Cameras"]
 size = Vector2( 100, 100 )
+msaa = 2
+usage = 3
 render_target_v_flip = true
 render_target_update_mode = 3
 
@@ -198,6 +200,8 @@ current = true
 
 [node name="Viewport2" type="Viewport" parent="Cameras"]
 size = Vector2( 100, 100 )
+msaa = 2
+usage = 3
 render_target_v_flip = true
 render_target_update_mode = 3