ColumnView: Restore runtime dispatch of removeItem
QML runtime dispatching of overloaded functions wasn't implemented for QObject types until Qt 6.5.3, so we can't rely on it yet. Revert to the old behavior of manual dispatch via QVariant conversions.
See also: https://codereview.qt-project.org/c/qt/qtdeclarative/+/481934
Partially reverts 9a9d9a20
Second commit:
ColumnView: Skip test for pop() without arguments
That method is only defined for one Item argument. There is simply no implementation for pop() without arguments. And even though writing such method would be trivial, the focus for now is to make tests usable for CI.
CC @mart @sporknife