It seems that in cases of grouped and attached properties we don't want
to create a new scope every time, but instead reuse the created one,
falling back to create if the scope doesn't exist
Consider:
```qml
QtObject {
myGroup.property1: 42 // case 1
myGroup.property2: "hello" // case 2
MyAttached.property1: 42 // case 3
MyAttached.property2: "hello" // case 4
}
```
The intuition tells that cases 1 and 2 should use the same shared
scope "myGroup" and so should cases 3 and 4 both use the same "MyAttached".
Creating a new scope each time for attached and grouped properties seems
erroneous
As a drive-by, add attached property type to tst_qmllint and test
that this still works after the changes to the related code
Change-Id: Ib1ae85b404a7954a3a3211cbd267c414b98ac59d
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Andrei Golubev