Fix geometry restoration check

MainWindow::wasWindowGeometrySaved() doesn't take into account the currently connected outputs. So
when Konsole starts after hotplugging a new output, wasWindowGeometrySaved() will erroneously return
true and resize(sizeHint()) in MainWindow::showEvent() won't be called thus resulting in Konsole
starting with wrong size.

This change makes Konsole take the current output layout into account when deciding whether the
geometry has been restored (logic was copied from KWindowConfig), however it indicates that we have
some fundamental issues in KMainWindow or KWindowConfig as it's a really messy way to determine
whether the previous state has been properly restored.

BUG: 460428


(cherry picked from commit 05892060)