Client: Unbatched propagation of size hints

As noted in https://codereview.qt-project.org/c/qt/qtwayland/+/412496 we commit() when propagateSizeHints() is called. Since minimum and maximum are set separately, this means they can also be committed separately, which can cause the invalid combination of min/max in QTBUG-102626 and QTBUG-103391.

The protocol error this would constitute has been fixed now and the impact should now be minimal given that the correct max size will be committed directly after, but the underlying issue still remains, so it would be good to investigate if we can do better, at least when both are updated during the same frame.