IO suspend methods are mixed into FutureController

[ilya-g]

Suspension functions for async IO are placed in FutureController due to:

• async IO must somehow interop with async futures.
• lack of extension suspend functions
• even if those extensions were possible, these methods are already member-extensions, so they can't be outside of the controller.

I suggest to wrap async IO operations into CompletableFuture's instead and perform await on these futures. This would require to write:

totalBytesRead += await(input.asyncRead(buf, totalBytesRead))

instead of

totalBytesRead += input.aRead(buf, totalBytesRead)

but IMO it's much more clear that a suspend point is introduced in the first example.

[elizarov]

Not applicable anymore. Async IO can be use in any async coroutine now.