Make sure that KItemListSizeHintResolver is always consistent

This was the root cause of bug 317827. The assert tried to make sure
that we never access KItemListSizeHintResolver from
KItemListViewLayouter inside the loop over the item ranges. This would
be dangerous because it might be in an inconsistent state - the removed
item ranges were removed step by step, so accessing the item size hints
before the operation was finished could lead to wrong results.

The solution is to insert/remove all item ranges immediately. A nice
side effect is that there are no sources of O(N^2) complexity in
KItemListSizeHintResolver any more if many item ranges are
inserted/removed.


FIXED-IN: 4.11.0
REVIEW: 111382