Add a permission for calls in a room

### Your use case

#### What would you like to do?

Have a room permission on creating calls.

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

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

### Have you considered any alternatives?

Use Element Web

### Additional context

Element Web already has this option for managing `org.matrix.msc3401.call.member` events or something like that, so I just toggle it there.

### Are you willing to provide a PR?

No

Start by locating the room-permission management and call handling entry points, then compare their behavior with Element Web's handling of org.matrix.msc3401.call.member events. Done should mean a room-level permission can control whether calls are created, with the behavior exposed consistently in the Android app.

Written by the indexing model from the issue text.