[wasm][fuzzer] Teach the fuzzers to deal with anyref and co

I don't know if there is another problem, but this change fixes all
problems in the test case. The fuzzer will eventually tell us if there
is another problem.

R=clemensh@chromium.org

Bug: chromium:1000503
Change-Id: I2f3ca9132e1b9e3f01e9b32604fb39b2272723f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1784278
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63547}

test/common/wasm/wasm-module-runner.cc

@@ -101,6 +101,12 @@ bool InterpretWasmModuleForTesting(Isolate* isolate,
       case kWasmF64:
         arguments[i] = WasmValue(0.0);
         break;
+      case kWasmAnyRef:
+      case kWasmFuncRef:
+      case kWasmExnRef:
+        arguments[i] =
+            WasmValue(Handle<Object>::cast(isolate->factory()->null_value()));
+        break;
       default:
         UNREACHABLE();
     }

test/fuzzer/wasm-fuzzer-common.cc

@@ -89,6 +89,12 @@ const char* ValueTypeToConstantName(ValueType type) {
       return "kWasmF32";
     case kWasmF64:
       return "kWasmF64";
+    case kWasmAnyRef:
+      return "kWasmAnyRef";
+    case kWasmFuncRef:
+      return "kWasmFuncRef";
+    case kWasmExnRef:
+      return "kWasmExnRef";
     default:
       UNREACHABLE();
   }