#3180. Add tests for createJSInteropWrapper() function

[sgrekhov]

Existing tests for JSExport also tests createJSInteropWrapper() function. So there are only few new tests here.

[eernstg]

Let's take another iteration on this one.

[srujzs]

nit: I'd maybe add a test where it's okay to have an exported class that has a member with an invalid type but it never exports it e.g.

class C {
  final D d; // not exported
  @JSExport()
  int get boo => d.bar();
  C(this.d);
}

[sgrekhov]

Added jsExport_A07_t03.dart. Please take another look.

[eernstg]

LGTM.