Dataflow: Deduplicate results when sinks accept multiple FlowStates.

[aschackmull]

Until now we've included the FlowState in the definition of PathNodeSink, but when sinks accept multiple states then this can show up as seemingly duplicate results. Projecting the state column away on sink nodes seems preferable.

[aschackmull]

Hmm, looks like we might actually introduce ~alert duplication~ potential false positives when the source is correlated with the sink state and the sink state is incorporated in the alert.