Refactor/vanilla store utils (#3138)

* feat(stores): use vanilla store utils

* fix(store-utils): keep dimensions if possible

* feat(utils): add nodeDimension and panBy utils

* fix(svelte): use correct updateDim func

* refactor(react): cleanup store

* chore(tests): use new imports

packages/react/src/container/Viewport/index.tsx

@@ -13,7 +13,7 @@ function Viewport({ children }: ViewportProps) {
   const transform = useStore(selector);
 
   return (
-    <div className="react-flow__viewport react-flow__container" style={{ transform }}>
+    <div className="react-flow__viewport xyflow__viewport react-flow__container" style={{ transform }}>
       {children}
     </div>
   );