feat(VDataIterator): propagate and add toggle-select-all event (#8975)

The toggle-select-all event from the VDataTable header mixin is propogated upwards and made
available in the VDataIterator. This event is explicitly triggered when all items are
selected/deselected with the top checkbox.

closes #8974

packages/api-generator/src/maps/v-data-iterator.js

@@ -19,6 +19,7 @@ const DataIteratorEvents = DataEvents.concat([
   { name: 'update:expanded', source: 'v-data-iterator', value: 'any[]' },
   { name: 'item-selected', source: 'v-data-iterator', value: '{ item: any, value: boolean }' },
   { name: 'item-expanded', source: 'v-data-iterator', value: '{ item: any, value: boolean }' },
+  { name: 'toggle-select-all', source: 'v-data-iterator', value: '{ value: boolean }' },
 ])
 
 const DataIteratorSlots = [

packages/vuetify/src/components/VDataIterator/VDataIterator.ts

@@ -142,6 +142,7 @@ export default Themeable.extend({
       })
 
       this.selection = selection
+      this.$emit('toggle-select-all', { value })
     },
     isSelected (item: any): boolean {
       return !!this.selection[getObjectValueByPath(item, this.itemKey)] || false

packages/vuetify/src/components/VDataIterator/__tests__/VDataIterator.spec.ts

@@ -172,13 +172,15 @@ describe('VDataIterator.ts', () => {
       { id: 'foo' },
       { id: 'bar' },
     ]
+    const toggleSelectAll = jest.fn()
 
     const wrapper = mountFunction({
       propsData: {
         items,
       },
       listeners: {
         input,
+        'toggle-select-all': toggleSelectAll,
       },
       scopedSlots: {
         header (props) {
@@ -200,6 +202,7 @@ describe('VDataIterator.ts', () => {
     await wrapper.vm.$nextTick()
 
     expect(input).toHaveBeenCalledWith(items)
+    expect(toggleSelectAll).toHaveBeenCalledWith({ value: true })
   })
 
   it('should update expansion from the outside', async () => {