Refactor GDScript/C# script templates logic to be editor-only

Not a full refactor as it still goes through ScriptLanguage so it's hacky,
but at least it can now compile without this.

modules/gdscript/editor/script_templates/CharacterBody2D/basic_movement.gd

@@ -0,0 +1,30 @@
+# meta-description: Classic movement for gravity games (platformer, ...)
+
+extends _BASE_
+
+
+const SPEED = 300.0
+const JUMP_VELOCITY = -400.0
+
+# Get the gravity from the project settings to be synced with RigidDynamicBody nodes.
+var gravity: int = ProjectSettings.get_setting("physics/2d/default_gravity")
+
+
+func _physics_process(delta: float) -> void:
+	# Add the gravity.
+	if not is_on_floor():
+		velocity.y += gravity * delta
+
+	# Handle Jump.
+	if Input.is_action_just_pressed("ui_accept") and is_on_floor():
+		velocity.y = JUMP_VELOCITY
+
+	# Get the input direction and handle the movement/deceleration.
+	# As good practice, you should replace UI actions with custom gameplay actions.
+	var direction := Input.get_axis("ui_left", "ui_right")
+	if direction:
+		velocity.x = direction * SPEED
+	else:
+		velocity.x = move_toward(velocity.x, 0, SPEED)
+
+	move_and_slide()