lang: Improve graph shape with speculative execution

Most of the time, we don't need to have a dynamic call sub graph, since
the actual function call could be represented statically as it
originally was before lambda functions were implemented. Simplifying the
graph shape has important performance benefits in terms of both keep the
graph smaller (memory, etc) and in avoiding the need to run transactions
at runtime (speed) to reshape the graph.

Co-authored-by: Samuel Gélineau <gelisam@gmail.com>

lang/funcs/structs/call.go

@@ -223,7 +223,7 @@ func (obj *CallFunc) replaceSubGraph(newFuncValue *full.FuncValue) error {
 	// methods called on it. Nothing else. It will _not_ call Commit or
 	// Reverse. It adds to the graph, and our Commit and Reverse operations
 	// are the ones that actually make the change.
-	outputFunc, err := newFuncValue.Call(obj.init.Txn, obj.ArgVertices)
+	outputFunc, err := newFuncValue.CallWithFuncs(obj.init.Txn, obj.ArgVertices)
 	if err != nil {
 		return errwrap.Wrapf(err, "could not call newFuncValue.Call()")
 	}