Use ephemeral events for live position updates
Live position updates should use ephemeral events to minimise delay and load on the room DAG.
Blocked by MSC: https://github.com/matrix-org/matrix-doc/pull/2477
Live position updates should use ephemeral events to minimise delay and load on the room DAG.
Blocked by MSC: https://github.com/matrix-org/matrix-doc/pull/2477