Connect interface

[Bilchreis]

• removes complicated event loop handling from SECoPNodeDevice class
• device instantiation, and connection to HW are now seperated
• device connection should be done using a context manager from now on:
  with RE present:

    with init_devices():
       cryo = SECoPNodeDevice(
           sec_node_uri="localhost:10769",
       )

instantiation without RE:

    async with init_devices():
        cryo = SECoPNodeDevice(
            sec_node_uri="localhost:10769",
        )