Replace most uses of Map by HashMap

* Map is unnecessary and inefficient in almost every case.
* Replaced by the new HashMap.
* Renamed Map to RBMap and Set to RBSet for cases that still make sense
  (order matters) but use is discouraged.

There were very few cases where replacing by HashMap was undesired because
keeping the key order was intended.
I tried to keep those (as RBMap) as much as possible, but might have missed
some. Review appreciated!

scene/resources/mesh_library.h

@@ -32,7 +32,7 @@
 #define MESH_LIBRARY_H
 
 #include "core/io/resource.h"
-#include "core/templates/map.h"
+#include "core/templates/rb_map.h"
 #include "mesh.h"
 #include "scene/3d/navigation_region_3d.h"
 #include "shape_3d.h"
@@ -56,7 +56,7 @@ public:
 		Ref<NavigationMesh> navmesh;
 	};
 
-	Map<int, Item> item_map;
+	RBMap<int, Item> item_map;
 
 	void _set_item_shapes(int p_item, const Array &p_shapes);
 	Array _get_item_shapes(int p_item) const;