REG: forceActiveFocus does not show virtual keyboard on Wayland

In Qt 5, calling forceActiveFocus() on a text element in Qt Quick would ensure the on-screen keyboard pops up, by calling showInputPanel() from the input method. In Qt 6, it does still call showInputPanel() but nothing shows up. Manually clicking to open the input panel still works fine with the same compositor and example.

Now, in Qt 5, forceActiveFocus() would have limited practical usability on its own, since the client cannot actually activate its own window, thus the opened keyboard will have no place to send the keyboard events.

But in Qt 6.3, we introduced the QtShell, which could possibly support this case, since window activation works there.

See QTBUG-94985 for an example that demonstrates the difference between Qt 5 and Qt 6.