[REG 6.6 → 6.8] qmlRestrictedType warning errorneously triggers for enum class

https://codereview.qt-project.org/c/qt/qtdeclarative/+/541680 changed the code we generate for enums to only apply the scoped marker if enums are registered with
"RegisterEnumClassesUnscoped" being set to false
(compare https://codereview.qt-project.org/c/qt/qtdeclarative/+/541680/6/src/qmltyperegistrar/qqmltypescreator.cpp#363)

This confuses the qmllint logic, which intends to warn about usages like
`Type.EnumName.EnumEntry`. However, while this is not mandatory with enum classes (unless said "RegisterEnumClassesUnscoped" is added), it' still possible.

We need to have a way to distinguish "scoped enums" from "only scoped enums".