Allow Space Owners to Set Predefined Sections

### Your use case

#### What would you like to do?

I would like for space owners to be able to set predefined sections for rooms in their spaces.

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

To allow extra customization/achieve familiarity that might be required coming from different apps. Might help brands too.

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

Allow space owners to set predefined sections that the user may then override/customize themselves further or turn off. Create a toggle in settings (that is opt-in) to disable all predefined sections on Element as well.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

No files, tests, or entry points are named. Start by locating the Element client settings and the room-section handling for Spaces; done means space owners can define opt-in predefined sections, users can override or disable them, and an Element setting can disable predefined sections globally.

Written by the indexing model from the issue text.