Way to use a CoroutineDispatcher as a RxJava Scheduler

[chrisbanes]

The rx2 artifact currently provides Scheduler.asCoroutineDispatcher() to use a Scheduler as a CoroutineDispatcher, but not the other way around.

Ideally I'd like to move over to the new IO and BackgroundDispatcher, and then move my Rx observables to use the same threads too.

[elizarov]

PR is welcome!

[chrisbanes]

I'll PR when I've done my KotlinConf slides (if no-one else grabs it first)

[elizarov]

Please do it for all reactive implementations (rx1, rx2, and reactor) if possible, just like asCoroutineDispatcher is implemented in all of them.

[Zeyad-37]

Any progress here ?