The RoomWidgetClient (embedded) is calling `/rtc/transports` without authentication

[BillCarsonFr]

The base _unstable_getRTCTransports is calling authedRequest for /rtc/transports.

When using the RoomWidgetClient (widget client), this will always result to a 401 Missing access token.

If we want widgets to support _unstable_getRTCTransports we need to introduce a new widget API action to forward to the host client, similar to other calls