As decided after discussions on the ML, QList should be the main type we're using in Qt 6, QVector an alias to it. Change the implementation to reflect that.
- Class implementation goes to qlist.h and is named QList
- qvector.h empty, only includes qlist.h
- using QVector = QList in qcontainerfwd.h
- Rename QVectorSpecialMethods to QListSpecialMethods