Rename several classes/behaviors to factory-style creators and adapt
call wiring and tests accordingly:
- Replace ConnectionManager class with createConnectionManager$ which
returns transports$, connectionManagerData$, connections$
- Convert MatrixLivekitMerger to createMatrixLivekitMembers$
(matrixLivekitMerger$)
- Rename sessionBehaviors$, localMembership$, localTransport$ to
createSessionMembershipsAndTransports$, createLocalMembership$,
createLocalTransport$
- Adjust participant types and hook up connectOptions$; expose join via
localMembership.requestConnect
- Update tests to use the new factory APIs
