Location sharing: Authorize only one beacon info per room and per member in the SDK

In the SDK you can see that starting multiple time live location sharing creates multiple `MXBeaconInfoSummary` for the current user in the `MXBeaconInfoSummaryMemoryStore` with live status.
- We should stop other beacon info before starting a new one in a room.
- We should only handle one beacon info per room for other users.

Start by locating MXBeaconInfoSummary and MXBeaconInfoSummaryMemoryStore in the SDK, then trace how live location sharing is started and how summaries are stored. Reproduce multiple live shares for the current user and multiple members in one room. Done means only one active beacon info remains per room for the sharing user and for each other member.

Written by the indexing model from the issue text.