Fix Flyout and TitleView Offset Measurements

[PureWeen]

Description of Change

Rework the Shell Flyout Templates/TitleView to mesh with .NET MAUI layout rules. The measuring and arranging of the templates needed to adjust for how margins are applied with the new layout system. This PR also streamlines the measuring/arranging so it's more part of the lifecycle instead of just randomly calling "remeasure" at different points in time hoping you'll eventually end up with things measured correctly.

This also decouples the Margin property from the SafeArea. Instead of applying the safe area to the margin we just apply the safe area to the container views if the user hasn't indicated they want to control the margins.

TitleView and Flyout Templates use the same platform containers which is why this PR addresses both.

Issues Fixed

Fixes #11679

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[mattleibow]

I saw things with parallax and toolbars and titles and things, so is it potentially related to: https://github.com/dotnet/maui/issues/9053

[PureWeen]

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