!str #15604: Removal of default fanout behavior
Merge pull request #15793 from drewhk/wip-15604-no-fanout-drewhk

!str #15604: Removal of default fanout
Prototype of FlowGraph
attachSource and attachSink
FlowGraph builder block
some nice syntax
PartialGraphFlow and syntactic sugar for attachSource and attachSink
Materialization traversal, MaterializedFlowGraph with sources and sinks
FlowGraphCompileSpec and some cleanup
fix review comments