[cfe] No error in if await e occurs ob extension type which is not subtype of Future

[sgrekhov]

CFE doesn't report expected errors below (analyzer does)

// SharedOptions=--enable-experiment=inline-class

extension type V0(Future<int> id) {}

extension type V1(Future<int> id) {}

extension type V2<T extends Future<Object>>(T id) {}

extension type V3(Future<int> id) implements V0 {}

main() async {
  V1 v1 = V1(Future<int>.value(42));
  await v1;
//      ^^
// [analyzer] unspecified
// [cfe] unspecified

  V2<Future<String>> v2 = V2(Future<String>.value("42"));
  await v2;
//      ^^
// [analyzer] unspecified
// [cfe] unspecified

  V3 v3 = V3(Future<int>.value(42));
  await v3;
//      ^^
// [analyzer] unspecified
// [cfe] unspecified
}

Failure log, test co19/LanguageFeatures/Extension-types/static_analysis_extension_types_A08_t02