Model ConnectionState as a discriminated union

The enum mixed our own lifecycle states with a copy of livekit-client's
connection states, and errors were smuggled through the same observable as
a separate union member. A discriminated union keeps the LiveKit state
nested under "authenticated", carries the error as data, and lets the
local member represent the time before a connection exists as an
"initializing" state instead of null.

src/state/CallViewModel/CallViewModel.ts

@@ -1662,9 +1662,9 @@ export function createCallViewModel$(
           returnObject.publishError = value.media;
         else if (
           typeof value.media === "object" &&
-          value.media.connection instanceof ElementCallError
+          value.media.connection.state === "error"
         )
-          returnObject.connectionError = value.media.connection;
+          returnObject.connectionError = value.media.connection.error;
         return returnObject;
       }),
     ),