Remove usage of DisplayInformation GetForCurrentView

[asklar]

Islands / winui 3 won't work well with DisplayInformation.GetForCurrentView , so we need to instead use something like XamlRoot.RasterizationScale and XamlRoot.Size, and listen to events from XamlRoot.Changed

[chrisglein]

APIs will only exist where islands are, like 19H1+ or WinUI3.
Some concerns raised here about multiple window/screen scenarios.
These are WinRT APIs, not WinUI APIs. Maybe addressed with Reunion?
We've raised these topics before, need to find the links.

[chrisglein]

Related issues: #4002 #3567

[asklar]

Reunion: microsoft/WindowsAppSDK#114

[chiaramooney]

Not something we plan to address on the Paper renderer as we move towards Fabric.
This behavior should be different on the non-XAML Fabric renderer.