update: a couple more perfomance related updates

* check for selected value inside Node instead of the wrapping renderer
* instead of "parsing" elements just return the current store.elements object
* use map funct to find index

Signed-off-by: Braks <78412429+bcakmakoglu@users.noreply.github.com>

examples/Stress/StressExample.vue

@@ -49,7 +49,7 @@ const updateElements = () => {
 }
 </script>
 <template>
-  <VueFlow :elements="elements" @load="onLoad" @elementsRemove="onElementsRemove" @connect="onConnect">
+  <VueFlow v-model="elements" @load="onLoad" @elementsRemove="onElementsRemove" @connect="onConnect">
     <MiniMap />
     <Controls />
     <Background />