[esnext] Fix various callsites to use is_resumable, not is_generator

src/objects-printer.cc

Index: src/objects-printer.cc
diff --git a/src/objects-printer.cc b/src/objects-printer.cc
index 7cb96aae558e480cc48f2e6033d505eaf4ce795c..183306583d051aff5fd65ec867fcdfc2a044a540 100644
--- a/src/objects-printer.cc
+++ b/src/objects-printer.cc
@@ -876,6 +876,8 @@ void JSFunction::JSFunctionPrint(std::ostream& os) {  // NOLINT
      << shared()->internal_formal_parameter_count();
   if (shared()->is_generator()) {
     os << "\n   - generator";
+  } else if (shared()->is_async()) {
+    os << "\n   - async";
   }
   os << "\n - context = " << Brief(context());
   os << "\n - literals = " << Brief(literals());