[ShadowContainer] unexpected layout behaviors

[Xiaoy312]

// TreeGraph taken on uwp (windows)
TextBox#SUT // Actual=336x55, Constraints=[0,NaN,∞]x[0,NaN,∞], HV=Stretch/Top, Foreground=#FF1C1B1F, CornerRadius=0, Margin=0, Padding=8, Opacity=1, Visibility=Visible, VisualStates=Normal|ButtonCollapsed
    ShadowContainer#RootPanel // Actual=336x55, Constraints=[0,NaN,∞]x[0,NaN,∞], HV=Stretch/Stretch, Foreground=#FF1C1B1F, CornerRadius=0, Margin=0, Padding=0, Opacity=1, Visibility=Visible
        Canvas#PART_Canvas // Actual=54x55, Constraints=[0,54,∞]x[0,55,∞], HV=Stretch/Stretch, Margin=0, Opacity=1, Visibility=Visible
            SKXamlCanvas // Actual=70x71, Constraints=[0,70,∞]x[0,71,∞], HV=Stretch/Stretch, Margin=0, Opacity=1, Visibility=Visible
            ContentPresenter // Actual=54x55, Constraints=[0,NaN,∞]x[0,NaN,∞], HV=Stretch/Stretch, Foreground=#FF1C1B1F, CornerRadius=0, Margin=0, Padding=0, Opacity=1, Visibility=Visible
                Grid#ContentPanel // Actual=54x55, Constraints=[0,NaN,∞]x[40,NaN,∞], HV=Stretch/Stretch, CornerRadius=4, Margin=0, Padding=8, Opacity=1, Visibility=Visible

PART_Canvas has a fixed size (based on its content-presenter), and doesnt stretch horizontally

[Xiaoy312]

on skia.gtk, ShadowContainer inside a disabled element's template also have alignment + clipped issue:

when comparing the visual tree, we can notice that the Height and Width value are not set:

[roubachof]

should be fixed by: #716