Deprecate delayFlow and delayEach

[elizarov]

This will make Flow API surface more orthogonal with less operators to remember. Both of them can be easily written without too much additional code and still produce quite readable and easy to understand code:

delayFlow(time) = onStart { delay(time) }
delayEach(time) = onEach { delay(time) }

[Augusent]

And what about prospective delayFlow(Flow) case? Wouldn't it be too verbose to follow onStart { ... } approach in this case?

[elizarov]

onStart { delay(xxx) } seems to be more explicit than delayFlow. Moreover, it is composable with all the delay extension. For example, if you use kotlinx-coroutines-jdk8 module you can write onStart { delay(1, TimeUnit.SECONDS) } without having to also introduce the corresponding extensions for all the flow operators.

[Augusent]

Yes, it surely is. But I meant more like delaySubscription(Observable) analogy from rx world. When a subscription (collection) of a flow is triggered after the first emission of the delayFlow's argument flow source.

[elizarov]

If you have a use-case for delaySubscription in mind, then please open a separate issue for it.