Consider providing access to the CoroutineScope in initialState

[rjrjr]

We've seen a number of use cases where we'd like to be able to start work in initialState and tear it down when the workflow session ends. You can almost do this with LifecycleWorker or runningSideEffect, except that those have no clean access to StateT, and so no easy way to hit the destruct button on whatever was kicked off by initialState.

It occurs to us that giving initialState the ability to launch work against the CoroutineScope that is managing a particular workflow session could be very convenient.

Needs thought, and a better description of exactly what use cases we're trying to enable.

cc @steve-the-edwards @ijwhelan to be more articulate than me. And @0legg if he's in a generous OSS mood.

[steve-the-edwards]

Duplicates #990 . Closing but will prioritize #990 .