Added release function to PoolVector::Access.

For clarity, assign-to-release idiom for PoolVector::Read/Write
replaced with a function call.
Existing uses replaced (or removed if already handled by scope)

editor/plugins/multimesh_editor_plugin.cpp

@@ -144,7 +144,7 @@ void MultiMeshEditor::_populate() {
 		}
 	}
 
-	w = PoolVector<Face3>::Write();
+	w.release();
 
 	PoolVector<Face3> faces = geometry;
 	ERR_EXPLAIN(TTR("Parent has no solid faces to populate."));