[turbofan] Introduce a TransitionElementsKind simplified operator.

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 5a9376e2d553403918c4f3498d427e366df1ee79..449c882e79c5c3ff9bf9fd1ea3cd55b8160b509f 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -2131,6 +2131,10 @@ class RepresentationSelector {
         }
         return;
       }
+      case IrOpcode::kTransitionElementsKind: {
+        VisitInputs(node);
+        return SetOutput(node, MachineRepresentation::kNone);
+      }
 
       //------------------------------------------------------------------
       // Machine-level operators.