A better group state transition API #285
Description
Being able to do group TX/RX concurrently with driving the ESM would be a better replacement for the request_into_* state change methods. This is a lower level API which hopefully #284 could be built on top of.
The real test/end goal for this API change is if a single SubDevice can fall out of OP back to INIT, then be brought back into OP, whilst the rest of the group stays in OP.
Bear in mind hotplug groups with this work, but I think that should probably a different bit of functionality. Unsure.
Is it possible to keep some/any/all of the current typestate API? If individual SubDevices should be handled, I think the answer is no.