use createSomething$ mathods instead of classes

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

src/state/localMember/LocalTransport.ts

@@ -50,7 +50,7 @@ interface Props {
  * @prop useOldestMember Whether to use the same transport as the oldest member.
  * This will only update once the first oldest member appears. Will not recompute if the oldest member leaves.
  */
-export const localTransport$ = ({
+export const createLocalTransport$ = ({
   scope,
   memberships$,
   client,