fix(useGetThreadId): make reactive value more responsive

[Antreesy]

☑️ Resolves

• Currently computed waits for $route to be updated. Since it's async, that delays interface update as well as some operations fail (as they're trying to proceed with old value)
• Now update it fast. But composable feels a bit redundant,..

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

No visual changes

🏁 Checklist

• 🌏 Tested with different browsers / clients:
  • Chromium (Chrome / Edge / Opera / Brave)
  • Firefox
  • Safari
  • Talk Desktop
  • Integrations with Files sidebar and other apps
  • Not risky to browser differences / client
• 🖌️ 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

[DorraJaouad]

Now update it fast. But composable feels a bit redundant,..

At this point, threadId can be just an item in global state (store)..

[ShGKme]

• Currently computed waits for $route to be updated. Since it's async

Note: reaction on reactive ref is also async