Allow for or extend checking connectedness of the provider

[lukashaertel]

Is your feature request related to a problem? Please describe.
I want to properly check the connectedness status of the provider, I am unsure if the connected flag of the WebrtcProvider is properly representative of this status, as it is true if the room is created, but not if any networking has been done.

Describe the solution you'd like
One of the following come to mind:

• The connection being properly represented as a flag so I can check it with e.g. promise.until from lib0
• Connection events to resolve new promises
• An async function in the provider connectedAsync that resolves if connected at call time or when the connection is established

Describe alternatives you've considered
Checking the connected flag, but as stated earlier, I am not sure if this is fully representative of what I would expect.

Additional context
I am not certain if a connection status can generally be determined in this configuration and if I am asking for a feature that cannot be implemented.

[lukashaertel]

I think the core issue is the I am having problems when I want to dynamically create and destroy providers but run into issues that a room is already in use because I cannot properly determine when all the room and connection management is completed.