There seems to be a bug in WinUI (see microsoft/microsoft-ui-xaml#2121)
that results in heterogeneous `ModernCollectionBasePanel` configured
with `DataTemplateSelector` and virtualization enabled to recycle a
container even if its `ContentTemplate` is wrong.
I considered few options of handling this:
* Disabling virtualization (by replacing item container template with
some non-virtualizing panel (e.g., `StackPanel`,
`VirtualizingStackPanel` with `VirtualizationMode`=`Standard`)
* Replacing `DataTemplateSelector` approach with `ChoosingItemContainer`
event handling approach, which allows you to manage the item container
(`ListViewItem`) allocation process.
I have chosen the last one, as it should limit the amount of
allocations, and might allow optimizations in the future.
The solution introduces:
* A container for `ListViewItem`s in the form of a map of sets:
* The key of this map is a data template (e.g., `TabItemDataTemplate`)
* The value in the set is the container
* `ChoosingItemContainer` event handler that looks for available item in
the container or creates a new one
* `ContainerContentChanging` event handler that returns the recycled
item to the container
Closes#9288
e02d9a48e3