Function dataflow::render::reduce::build_monotonic

fn build_monotonic<G>(
    collection: Collection<G, (Row, Row)>, 
    _: MonotonicPlan
) -> Arranged<G, TraceAgent<OrdValSpine<Row, Row, <G as ScopeParent>::Timestamp, Diff, usize>>> where
    G: Scope,
    G::Timestamp: Lattice, 

Build the dataflow to compute and arrange multiple hierarchical aggregations on monotonic inputs.