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.

gui/rich_text_bbcode/project.godot

@@ -27,7 +27,7 @@ window/vsync/vsync_mode=0
 [input]
 
 toggle_pause={
-"deadzone": 0.5,
+"deadzone": 0.2,
 "events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":-1,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":4194313,"physical_keycode":0,"key_label":0,"unicode":0,"echo":false,"script":null)
 ]
 }

gui/rich_text_bbcode/rich_text_bbcode.tscn

@@ -56,7 +56,7 @@ Left alignment is default,[center]but center alignment is supported,[/center][ri
 
 [fill][dropcap font_size=48 color=yellow margins=0,-10,0,-12]F[/dropcap]ill alignment is also supported, and allows writing very long text that will end up fitting the horizontal space entirely with words of joy. Drop caps are also supported. When using a drop cap, the first character of a paragraph is made larger, taking up several lines of text and optionally using a specific font or color.[/fill]
 
-Several effects are also available:    [wave]Wave[/wave]    [tornado]Tornado[/tornado]    [shake]Shake[/shake]    [fade start=67 length=7]Fade[/fade]    [rainbow]Rainbow[/rainbow]
+Several effects are also available:    [pulse]Pulse[/pulse]    [wave]Wave[/wave]    [tornado]Tornado[/tornado]    [shake]Shake[/shake]    [fade start=75 length=7]Fade[/fade]    [rainbow]Rainbow[/rainbow]
 
 [table=2]
 [cell border=#fff3 bg=#fff1]