refactor(VTreeview): avoid re-render by opened & respect openAll

[yuwu9145]

Keep the fix for #19919
Add cy tests & fixes #20024
fixes #19997

Description

Markup:

<template>
  <v-treeview
    :items="items"
  />
</template>

<script>
  export default {
    computed: {
      items: () => {
        const GetChildren = id => {
          const nodes = []
          for (let i = 0; i < 100; i++) {
            nodes.push({
              id: `${id}-${i}`,
              title: `Example child item ${i}`,
            })
          }
          return nodes
        }
        const nodes = []
        for (let i = 0; i < 2; i++) {
          nodes.push({
            id: i,
            title: `Example item ${i}`,
            children: GetChildren(i),
          })
        }
        return nodes
      },
    },
    methods: {
openedUpdate: function(e) {
  this.opened = e;
  console.log('openedUpdate', e)
}
    },
    data: () => ({
      opened: [],
    }),
  }
</script>