Creates an instance of a cold Flow that subscribes to the given ObservableValue and emits its values as they change. The resulting flow is conflated, meaning that if several values arrive in quick succession, only the last one will be emitted. Since this implementation uses ObservableValue.addListener, even if this ObservableValue supports lazy evaluation, eager computation will be enforced while the flow is being collected. All the calls to JavaFX API are performed in Dispatchers.JavaFx. This flow emits at least the initial value.
Adjacent applications of flowOn, buffer, conflate, and produceIn to the result of
asFlow are fused. conflate has no effect, as this flow is already conflated; one can use buffer to change that instead.