=str #16233 adds ReadAll for FlexiMerge

With one discussion point - what should we expose in java/scala apis? `Array` in both - in scala then we cant pattern match on it, but maybe that's not important anyway hm

Refs #16233
would this be possible?

    val values: Map[InputHandle, Any] = inputHandles.collect { 
      case input if !inputBunch.isCancelled(input.portIndex) => input -> inputBunch.dequeue(input.portIndex)
    }