Implement the new group call designs (Element Call) 2/2

[fkwp]

continuation of #23107

Figma

• Call banner in the room header
  • Room call banner matrix-org/matrix-react-sdk#9378
  • See designs
  • Should only be shown when there's an ongoing call, but its tile is off-screen. always be visible when there is an ongoing call in the room.
  • Needs to be hidden if the user is already in the call or looking at the lobby, or if a location share banner is being displayed (since we don't want double banners)
• Prevent the user from joining if they've already joined from another device
  • Disconnect other connected devices (of the same user) when joining an Element call matrix-org/matrix-react-sdk#9379
  • Or, even better, we could automatically disconnect the user on their other device when you join. This prevents you from getting in a situation where you can't join because of a stuck device.