GUI: do not interfere with saved sizes when restoring geometry

restoreGeometry() and restoreState() manipulate sizes and state of certain
widgets, and there are slots connected to signals which these widgets emit
which, in the end, lead to updating the saved state on disk, which is a wrong
thing to do here.

CCBUG: 323715
GUI: fix the maximized state when restoring geometry

This is a workaround for https://bugreports.qt-project.org/browse/QTBUG-30636.

Thanks to Thomas for comments.

BUG: 323715
REVIEW: 112182
Merge branch 'bug-323715'