Reconnect robustness, expose connection state. (#5869)

* Reconnect robustness, expose connection state.

- Expose connection status as rflink.connection_status state.
- Handle alternative timeout scenario.
- Explicitly set a timeout for connections.
- Error when trying to send commands if disconnected.
- Do not block component setup on gateway connection.

* Don't use coroutine where none is needed.

* Test disconnected behaviour.

* Use proper conventions for task creation.

* Possibly fix test race condition?

* Update hass import style