Safe area layout supporting for NavigationPage and TabbedPage

[ForkBug]

Description

Please add Safe area layout supporting for NavigationPage and TabbedPage. Therefore we could control Safe area behavior if we use NavigationPage or TabbedPage as the main page

Public API Changes

Add SafeAreaEdges to NavigationPage and TabbedPage

Intended Use-Case

If a NavigationPage or TabbedPage is used as the main page of the app, we want to control the safe area behavior of the page

[MitchBomcanhao]

In FlyoutPage, the old ios:Page.UseSafeArea="true" implementation is marked as obsolete, but if you add SafeAreaEdges="All" it also gets highlighted as NotFound.