[debugger] fix stepping over await calls for ignition generators.

src/debug/debug.h

Index: src/debug/debug.h
diff --git a/src/debug/debug.h b/src/debug/debug.h
index 1635621349b6e5ffcb74496feee0cf41f0d5fb77..eb2708c32f36ee802463e529b07fb57b2d171b54 100644
--- a/src/debug/debug.h
+++ b/src/debug/debug.h
@@ -38,9 +38,10 @@ enum StepAction : int8_t {
   StepNext = 1,   // Step to the next statement in the current function.
   StepIn = 2,     // Step into new functions invoked or the next statement
                   // in the current function.
-  StepFrame = 3   // Step into a new frame or return to previous frame.
-};
+  StepFrame = 3,  // Step into a new frame or return to previous frame.
 
+  LastStepAction = StepFrame
+};
 
 // Type of exception break. NOTE: These values are in macros.py as well.
 enum ExceptionBreakType {