Convert physics test projects to 4.0

[pouleyKetchoupp]

Everything seems to work except for a few specific issues.
I'm listing all the changes I've made in case it helps for future conversions and for keeping track of possible issues for users.

General changes:

• Control nodes: margin_* renamed to offset_*
• Annotations: @export, @export_range, @tool, @onready
• Some export variables need to be static typed since export annotations don't include a type anymore
• Signal connections using Callable
• Variable setters and getters using set/get functions instead of setget keyword
• Some variable setters need to be changed to avoid a stack overflow
• Renamed 3D classes referenced in gdscript
• Using await instead of yield, no more completed signal
• Using super calls in built-on functions to call the parent script when needed
• Uppercase color constants
• Renamed empty() to is_empty() in several classes
• Manual conversion from StringName to String
• Renamed pause_mode to process_mode
• Can't set material_override in GeometryInstance3D, need to use set_surface_override_material() in MeshInstance3D instead
• Replace ImmediateGeometry node with MeshInstance3D node and ImmediateMesh resource
• Renamed BUTTON_* to MOUSE_BUTTON_*
• Renamed scancode to keycode
• Renamed OS.get_ticks_usec() to Time.get_ticks_usec()
• Renamed instance() to instantiate()
• Use DisplayServer.window_get_mode() and DisplayServer.window_set_mode() instead of OS.window_fullscreen
• Project setting window/stretch/mode: canvas_item instead of 2d
• Project input mapping has to be set again by hand, all keys are missing
• Can't make a custom script that extends Slider anymore, need to use HSlider or VSlider
• TileMap collisions were offseted and cell size was reset

Physics specific changes:

• RectangleShape2D node: extents renamed to size and values doubled
• KinematicBody -> CharacterBody for character controllers
• KinematicBody -> StaticBody with kinematic_motion for moving platforms
• Renamed physics classes with 2D and 3D suffix in gdscript
• Renamed GodotPhysics engine string to GodotPhysics2D and GodotPhyics3D
• Renamed MODE_RIGID to MODE_DYNAMIC in RigidBody
• Properties instead of arguments in move_and_slide()
• 3D capsule is up by default
• One directional collision layers require new setup in some cases
• Adjustments for RigidBody2D due to increased default gravity
• RayShape2D/RayShape3D have been removed

Notes:

• Regression in "Character - TileMap": one-way collision are not working at the moment (PR: Fix one-way collision in Tilemap godot#51259).
  edit: fix is merged
• Regression in "Character - Pixels": test case "floor detection with motion changes" fails.
  edit: just made a typo when updating a rectangle size, fixed now.
• Rendering issue in "Character - Pixels": it was previously using a Viewport node with lower resolution. It's all blurry now and I didn't find how to properly set pixelated rendering in 4.0.
  edit: fixed by setting size_2d_override and size_2d_override_stretch in SubViewport

[pouleyKetchoupp]

Switched to draft because I noticed a couple things I can still fix before merging.

[pouleyKetchoupp]

Everything should be ready now, I've fixed the last remaining issues.

[pouleyKetchoupp]

I've just updated the 2D character tests with needed changes from godotengine/godot#51027 and also replaced references to Kinematic Body to Character Body in the scripts and UI.

[pouleyKetchoupp]

Updated with changes from godotengine/godot#51490: no more ray shapes and added new CharacterBody parameters instead.