Adding existing rooms to spaces has a confusing UX

### Steps to reproduce

1. Check any of the 3 ways of adding rooms to a space

### Outcome

#### What did you expect?

Seeing an option to add existing rooms to a space

#### What happened instead?

You can either create a new room or use the public room list. However, there is no more way to add existing rooms that are private.

### Operating system

Windows 11

### Browser information

Firefox 95.0 (64-bit)

### URL for webapp

staging.element.io

### Application version

Version von Element: 23b21c940c68-react-8f3ea977293b-js-3eaed304466a Version von Olm: 3.2.8

### Homeserver

nordgedanken.dev

### Will you send logs?

No