When leaving a space and leaving some rooms, show a "select all" option in the list of rooms

### Your use case

#### What would you like to do?

When leaving a space and leaving some rooms, I would like to be able to click a "Select all" button/check box that checks the box for every room in the list.

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

Sometimes (fairly often actually) when I leave a space I want to leave every room _except_ for a few. With the current UI it means I have to manually select all the rooms but the one or two I don't want to leave.

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

Add a "Select all" button/check box at the top of the list of rooms in the modal (position is important so that I don't need to scroll aaaaall the way down to find it).

### Have you considered any alternatives?

_No response_

### Additional context

_No response_