[cxx-interop] Import ObjCPropertyDecl of type NS_OPTIONS fields a struct type

Try importing ObjCPropertyDecl field types the C++-Interop-NS_OPTIONS
way. This will fix cases such as:

```
import UIKit

func f(gesture: UISwipeGestureRecognizer,
       direction: UISwipeGestureRecognizer.Direction) {
  gesture.direction = direction // error
}
```

because it will make sure the field inside class UIGestureRecognizer is
of the enum-struct type and not the typedef-rawValue type when importing
an ObjC class.

Author: plotfi

lib/ClangImporter/ImportDecl.cpp

@@ -5214,7 +5214,11 @@ namespace {
         }
       }
 
-      auto importedType = Impl.importPropertyType(decl, isInSystemModule(dc));
+      auto fieldType = decl->getType();
+      ImportedType importedType = tryImportOptionsTypeForField(fieldType, Impl);
+
+      if (!importedType)
+        importedType = Impl.importPropertyType(decl, isInSystemModule(dc));
       if (!importedType) {
         Impl.addImportDiagnostic(
             decl, Diagnostic(diag::objc_property_not_imported, decl),