refactor(hydroflow_lang): remove reference edges, reverts hydro-proje…

…ct#1017 hydro-project#1041 (hydro-project#1160)

hydroflow_datalog_core/src/snapshots/hydroflow_datalog_core__tests__aggregations_fold_keyed_expr@datalog_program.snap

@@ -9,7 +9,7 @@ fn main() {
             use hydroflow::{var_expr, var_args};
             let mut df = hydroflow::scheduled::graph::Hydroflow::new();
             df.__assign_meta_graph(
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+                "{\"nodes\":[{\"value\":null,\"version\":0},{\"value\":null,\"version\":2},{\"value\":{\"Operator\":\"unique :: < 'tick > ()\"},\"version\":1},{\"value\":null,\"version\":2},{\"value\":null,\"version\":2},{\"value\":{\"Operator\":\"unique :: < 'tick > ()\"},\"version\":1},{\"value\":{\"Handoff\":{}},\"version\":3},{\"value\":{\"Operator\":\"source_stream (ints)\"},\"version\":1},{\"value\":{\"Operator\":\"for_each (| v | result . send (v) . unwrap ())\"},\"version\":1},{\"value\":{\"Operator\":\"map (| row : (_ , _ ,) | ((row . 0 % 2 ,) , (row . 1 ,)))\"},\"version\":1},{\"value\":{\"Operator\":\"fold_keyed :: < 'tick , (_ ,) , (Option < _ > ,) > (| | (None ,) , | old : & mut (Option < _ > ,) , val : (_ ,) | { old . 0 = if let Some (prev) = old . 0 . take () { Some (prev + val . 0) } else { Some (val . 0) } ; })\"},\"version\":1},{\"value\":{\"Operator\":\"map (| (g , a) : ((_ ,) , _) | (g . 0 , a . 0 . unwrap () ,))\"},\"version\":1}],\"graph\":[{\"value\":null,\"version\":0},{\"value\":[{\"idx\":7,\"version\":1},{\"idx\":2,\"version\":1}],\"version\":3},{\"value\":null,\"version\":2},{\"value\":[{\"idx\":11,\"version\":1},{\"idx\":5,\"version\":1}],\"version\":3},{\"value\":[{\"idx\":6,\"version\":3},{\"idx\":10,\"version\":1}],\"version\":3},{\"value\":null,\"version\":2},{\"value\":[{\"idx\":5,\"version\":1},{\"idx\":8,\"version\":1}],\"version\":3},{\"value\":null,\"version\":2},{\"value\":[{\"idx\":10,\"version\":1},{\"idx\":11,\"version\":1}],\"version\":1},{\"value\":[{\"idx\":9,\"version\":1},{\"idx\":6,\"version\":3}],\"version\":3},{\"value\":[{\"idx\":2,\"version\":1},{\"idx\":9,\"version\":1}],\"version\":3}],\"ports\":[{\"value\":null,\"version\":0},{\"value\":[\"Elided\",\"Elided\"],\"version\":3},{\"value\":null,\"version\":0},{\"value\":[\"Elided\",\"Elided\"],\"version\":3},{\"value\":[\"Elided\",\"Elided\"],\"version\":3},{\"value\":null,\"version\":0},{\"value\":[\"Elided\",\"Elided\"],\"version\":3},{\"value\":null,\"version\":0},{\"value\":[\"Elided\",\"Elided\"],\"version\":1},{\"value\":[\"Elided\",\"Elided\"],\"version\":3},{\"value\":[\"Elided\",\"Elided\"],\"version\":3}],\"node_subgraph\":[{\"value\":null,\"version\":0},{\"value\":null,\"version\":0},{\"value\":{\"idx\":2,\"version\":1},\"version\":1},{\"value\":null,\"version\":0},{\"value\":null,\"version\":0},{\"value\":{\"idx\":1,\"version\":1},\"version\":1},{\"value\":null,\"version\":0},{\"value\":{\"idx\":2,\"version\":1},\"version\":1},{\"value\":{\"idx\":1,\"version\":1},\"version\":1},{\"value\":{\"idx\":2,\"version\":1},\"version\":1},{\"value\":{\"idx\":1,\"version\":1},\"version\":1},{\"value\":{\"idx\":1,\"version\":1},\"version\":1}],\"subgraph_nodes\":[{\"value\":null,\"version\":0},{\"value\":[{\"idx\":10,\"version\":1},{\"idx\":11,\"version\":1},{\"idx\":5,\"version\":1},{\"idx\":8,\"version\":1}],\"version\":1},{\"value\":[{\"idx\":7,\"version\":1},{\"idx\":2,\"version\":1},{\"idx\":9,\"version\":1}],\"version\":1}],\"subgraph_stratum\":[{\"value\":null,\"version\":0},{\"value\":1,\"version\":1},{\"value\":0,\"version\":1}],\"node_singleton_references\":[{\"value\":null,\"version\":0},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1},{\"value\":[],\"version\":1}],\"node_varnames\":[{\"value\":null,\"version\":0},{\"value\":null,\"version\":0},{\"value\":\"ints_insert\",\"version\":1},{\"value\":null,\"version\":0},{\"value\":null,\"version\":0},{\"value\":\"result_insert\",\"version\":1}],\"flow_props\":[{\"value\":null,\"version\":0}],\"subgraph_laziness\":[{\"value\":null,\"version\":0}]}",
             );
             df.__assign_diagnostics("[]");
             let (hoff_6v3_send, hoff_6v3_recv) = df