Chore(Vue3): Migrate to mitt

[DorraJaouad]

Part of #9448

• Replace EventBus with mitt.
• As mitt emitter doesn't have once method, the latter was replaced like :

const handler = () => {
	function()
	emitter.off('event', handler)
}

emitter.on('event', handler) 

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

no visual changes

🏁 Checklist

• 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• 🖥️ Tested with Desktop client or should not be risky for it
• 🖌️ Design was reviewed, approved or inspired by the design team
• ⛑️ Tests are included or not possible
• 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

---

[ShGKme]

• As mitt emitter doesn't have once method, the latter was replaced like :

Or we can add a new method to the event bus aka

const EventBus = mitt()
EventBus.once = function(type, handler) {
  this.on(type, ...)
}