Feature: Allow manually placing town buildings in scenario editor.

House picker is accessed from the Landscaping toolbar as there is no town toolbar.

Once placed these houses behave like any other and can be removed by players and towns.

Uses the unified picker system, so also supports used/saved favourites. As town building don't have class labels, town zones are use to imitate them.

src/town_cmd.cpp

@@ -4066,3 +4066,8 @@ extern const TileTypeProcs _tile_type_town_procs = {
 	GetFoundation_Town,      // get_foundation_proc
 	TerraformTile_Town,      // terraform_tile_proc
 };
+
+std::span<const DrawBuildingsTileStruct> GetTownDrawTileData()
+{
+	return _town_draw_tile_data;
+}