TileMap: Make collision visibility opt-in

Supersedes #47204, see discussion there.

doc/classes/TileMap.xml

@@ -326,7 +326,7 @@
 		<member name="occluder_light_mask" type="int" setter="set_occluder_light_mask" getter="get_occluder_light_mask" default="1">
 			The light mask assigned to all light occluders in the TileMap. The TileSet's light occluders will cast shadows only from Light2D(s) that have the same light mask(s).
 		</member>
-		<member name="show_collision" type="bool" setter="set_show_collision" getter="is_show_collision_enabled" default="true">
+		<member name="show_collision" type="bool" setter="set_show_collision" getter="is_show_collision_enabled" default="false">
 			If [code]true[/code], collision shapes are shown in the editor and at run-time. Requires [b]Visible Collision Shapes[/b] to be enabled in the [b]Debug[/b] menu for collision shapes to be visible at run-time.
 		</member>
 		<member name="tile_set" type="TileSet" setter="set_tileset" getter="get_tileset">

scene/2d/tile_map.h

@@ -80,7 +80,7 @@ private:
 	CollisionObject2D *collision_parent;
 	bool use_kinematic;
 	Navigation2D *navigation;
-	bool show_collision = true;
+	bool show_collision = false;
 
 	union PosKey {