Extend UseSafeArea to Android (and other platforms)

[borrmann]

Description

On iOS, ContentPage has the property UseSafeArea so the entire screen can be used.
This should work on Android as well and the window should be extended to use the NavigationBar and StatusBar.
In fact there is also a Bug in Android with Shell, that the window cant be extended to use the space of the StatusBar

Window.SetDecorFitsSystemWindows(false); doesnt work with AppShell!

Public API Changes

UseSafeArea should work on Android as well

Intended Use-Case

UseSafeArea=False, when you want pages on the whole Screen on both iOS and Android (and maybe other platforms too)

[ghost]

We've added this issue to our backlog, and we will work to address it as time and resources allow. If you have any additional information or questions about this issue, please leave a comment. For additional info about issue management, please read our Triage Process.