[SDK] Move SFU authentication into livekit/auth and choose the endpoint by role

The OpenID flow moves to src/livekit/auth/openID.ts with the SFU config
types in a sibling file, takes an options object, and replaces the
MatrixRTC mode with the role we take on the transport plus the session's
slot ID instead of a hard-coded m.call#ROOM.

This changes behaviour: publishers on a livekit_service_url transport
always use the legacy /sfu/get endpoint, so that subscribers can predict
their user:device participant identity, and subscribers always use the
default /get_token endpoint. The MatrixRTC mode no longer influences which
endpoint is used.

On the SDK this lands as sdk/src/media-backend/livekit/auth/ with the connection map, the discriminated connection state and the client-server API flow of the following commits of element-hq/element-call#4331, which rewrite the same files:
- Model ConnectionState as a discriminated union
- Show the whole transport in debug UI and logs (SDK part)
- Let the publishing Connection authenticate itself
- Reduce ConnectionManager to a ConnectionMap
- Use the unstable LiveKit transport type
- Identify transports by server name as well as URLs
- Get SFU tokens and delegate delayed leaves through the MSC4195 CS API
- Fall back to get_token as subscriber on widget API errors
- Share a connection between homeservers using the same JWT service
- Make the auth choice mode independent again

Co-authored-by: Johannes Marbach <n0-0ne+github@mailbox.org>
(cherry picked from commit adb380cd9ed108856e42d992fc03ced8c44f1e56)

sdk/index.ts

@@ -63,8 +63,8 @@ export {
 } from "./src/media-backend/livekit/LivekitBackend";
 // For a host that creates LiveKit tracks itself, such as a preview before joining
 export { convertToLivekitProcessor } from "./src/media-backend/livekit/videoProcessor";
-// For a developer panel to check a transport url before using it
+// For a developer panel to check a transport before using it
 export {
-  getSFUConfigWithOpenID as authenticateWithTransport,
-  type TokenEndpoint,
-} from "./src/media-backend/livekit/openIDSFU";
+  getSFUConfig as authenticateWithTransport,
+  type GetSFUConfigParams as AuthenticateWithTransportParams,
+} from "./src/media-backend/livekit/auth";