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/remoteMembers/Connection.ts

@@ -13,7 +13,8 @@ import {
   ConnectionError,
   type ConnectionState as LivekitConenctionState,
   type Room as LivekitRoom,
-  type Participant,
+  type LocalParticipant,
+  type RemoteParticipant,
   RoomEvent,
 } from "livekit-client";
 import { type LivekitTransport } from "matrix-js-sdk/lib/matrixrtc";
@@ -32,7 +33,7 @@ import {
   SFURoomCreationRestrictedError,
 } from "../../utils/errors.ts";
 
-export type PublishingParticipant = Participant;
+export type PublishingParticipant = LocalParticipant | RemoteParticipant;
 
 export interface ConnectionOpts {
   /** The media transport to connect to. */