Integrate with KotlinX Immutable Collections, add `Flow.toMap`

[Laxystem]

This could be done fairly easily:

suspend fun <T> Flow<T>.toPersistentList() = emptyPersistentHashList<T>().mutate { toList(it) }

public suspend fun <K, V, M : MutableMap<in K, in V>> Flow<Pair<K, V>>.toMap(destination: M): M {
    collect { (key, value) ->
        destination[key] = value
    }
    return destination
}

suspend fun <K, V> Flow<Pair<K, V>>.toPersistentHashMap() = emptyPersistentHashMap<Pair<K, V>>().mutate { toMap(it) }

I used mutate instead of toXxx(mutableXxxOf()).toPersistentXxx() as the mutate function uses builders, that KotlinX Immutable Collections can optimize.

A nice addition to complement the toMap that is necessary for this suggestion would be a Map.asFlow.

[dkhalanskyjb]

toPersistentList is something that we can add according to the decision in #4212 (comment). toPersistentHashMap is questionable, because we don't even have that for List or Sequence, and Flow is the next step.

cc @qurbonzoda

[Laxystem]

toPersistentHashMap is questionable, because we don't even have that for List or Sequence, and Flow is the next step.

I'd argue that we should have it for them as well, and that there's no reason not to add them to Flow in the meanwhile.

[qurbonzoda]

I am wondering if this integration requires publishing a separate artifact (perhaps in kx-collections-immutable) with relevant functions?

[Laxystem]

@qurbonzoda it does, unless you want to introduce a dependency on it.