Simplify all view model APIs and always return G_TYPE_OBJECT as the
item-type for every model.
It turns out nobody uses item-type anyway.
So instead of adding lots of APIs, forcing people to think about it and
trying to figure out how to handle filter or map models that modify item
types, just having an easy life is a better approach.
All the models need to be able to deal with any type of object going
through anyway.
In particular, track which items remain in ::items-changed
signal emissions.
But the main use case is sorting, which causes items-changed(0, n, n)
to be emitted.
This is not just about consistency with other functions.
It is about avoiding reentrancy problems.
GtkListBase first doing an unselect_all() will then force the
SelectionModel to consider a state where all items are unselected
(and potentially deciding to autoselect one) and then cause a
"selection-changed" emission that unselects all items and potentially
updates all the list item widgets in the GtkListBase to the unselected
state.
After this, GtkListBase selects new items, but to the SelectionModel and
the list item widgets this looks like an enitrely new operation and
there is no way to associate it with the previous state, so the
SelectionModel cannot undo any previous actions it took when
unselecting.
And all listitem widgets will now think they were just selected and
start running animations about selecting.
When exclusive is TRUE, we would not always emit a
::selection-changed signal that covers all the items
that were unselected.
This commit includes a test.
