Window size behavior

When setting the width and height, the final size is larger than the one set when the TitleBar is displayed.

Avalonia behavior

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
        x:Class="Sandbox.MainWindow"
        Width="1024" Height="800">
</Window>

WPF behavior:

<Window x:Class="WpfApp3.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp3"
        mc:Ignorable="d"
        Title="MainWindow" Height="800" Width="1024">
    <Grid>
        
    </Grid>
</Window>

[kekekeks]

I believe we are using client size here for consistency reasons. i. e. one would expect 100x100 Border to fit into 100x100 window. We should probably have separate properties for the full window size for platforms that support it.

[maxkatz6]

We now have window.FrameSize property that includes window decoration bounds. Readonly. Width and Height are still defining client size, as per reasons above.