Add Meta-Spaces like in Web

### Your use case

#### What would you like to do?

I would like to have the ability to show all of my DMs, all of my Favourites and all of my rooms that are not part of any space in one place each.

#### Why would you like to do it?

Parity with web, makes it easier to use the full potential of spaces.

#### How would you like to achieve it?

Use Meta-Spaces like in in Web that are shown on top of the Spaces list after Home and each group my rooms as described.
Since it would be annoying to have four tabs in each of these Meta-Spaces, this would greatly benefit from [getting rid of the different horizontal tabs and merging them](https://github.com/vector-im/element-ios/issues/5960).

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

Start by comparing the current iOS Spaces list with the Web behavior described in the issue, then read issue #5960 about merging the horizontal tabs. Done means Meta-Spaces appear above the Spaces list after Home and group all DMs, favourites, and rooms outside any space as requested.

Written by the indexing model from the issue text.