Add aggregated unread indicator for spaces in the new layout

[mnaturel]

Steps to reproduce

With the new layout, notification counter badge is missing in the floating button to open the spaces list bottom sheet.

Outcome

What did you expect?

See a counter badge on the floating action button which opens the spaces list bottom sheet.

What happened instead?

No counter badge on the floating action button which opens the spaces list bottom sheet is visible.

Your phone model

No response

Operating system version

No response

Application version and app store

No response

Homeserver

No response

Will you send logs?

No

Are you willing to provide a PR?

Yes