refactor: Migrate format tests to Scripts API

[johnsoncodehk]

Using the Scripts API, we have an easier way to execute formatting.

import { createFormatter } from '@volar/kit'; // 1.5.3
import { resolveConfig } from '@vue/language-service'; // 1.7 pre-release / 2.0

const volarConfigForVue = resolveConfig({ /* base setup from volar.config.js */});
const formatter = createFormatter(volarConfigForVue);
const result = await formatter.formatCode('<template>{{msg}}</template>', 'vue', { insertSpaces: false, tabSize: 4 });

console.log(result); // <template>{{ msg }}</template>