Implement setData()/shallowMount with initialData for components using the Composition API / <script setup>

[KCMertens]

This PR adds support for setData() and shallowMount({initialData: ...}) for components defined using the <script setup> syntax.

To my surprise this isn't supported yet, yet it seems like an important tool, especially when refactoring components from the Options API to the Composition API.

E.g. the following test would fail:

ScriptSetup.vue

<script setup lang="ts">
import { ref } from 'vue'
const count = ref(0)
const inc = () => { count.value++ }
</script>

<template>
  <button @click="inc()">{{ count }}</button>
</template>

ScriptSetup.spec.ts

it('updates data on a component using <script setup>', async () => {
	const wrapper = shallowMount(ScriptSetup)
	await wrapper.setData({ count: 20 })
	expect(wrapper.html()).toContain('20')
})

I've added a few tests to the existing setData suite, and everything seems to work as expected.

Note

All variables from a <script setup> / the component's setup() function seem to be placed in a single proxy/object by the Vue compiler/runtime.

This means setData() can technically be used to overwrite everything defined or imported in the setup script/function, not just the refs and reactives.
I don't think there is an easy way to decide what should and should not be allowed to be overwritten, so for now allow everything.

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[cexbrayat]

Thank you for your contribution 👍