Border can set multi StrokeThickness; Frame can set multi CornerRadius

Description

in WPF Border can set multi value of BorderThickness and CornerRadius

in MAUI Border only accept 1 value of StrokeThickness
Frame only accept 1 value of CornerRadius

Public API Changes

WPF XAML

        <Border BorderBrush="Blue" BorderThickness="1,2,3,4" CornerRadius="1,2,3,4">
            <Grid>
                <TextBlock Text="Label" />
            </Grid>
        </Border>

MAUI XAML

    <Grid BackgroundColor="Blue">
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>
        <Border Stroke="Black" StrokeThickness="1,2,3,4" Grid.Row="0">
            <!-- copy from https://docs.microsoft.com/en-us/dotnet/maui/user-interface/controls/border -->
            <Border.StrokeShape>
                <RoundRectangle CornerRadius="1,2,3,4" />
            </Border.StrokeShape>
            <Grid>
                <Label Text="Label" />
            </Grid>
        </Border>
        <Frame BorderColor="Gray" CornerRadius="1,2,3,4" Grid.Row="1">
            <Label Text="Label" />
        </Frame>
    </Grid>

Intended Use-Case

Would like Border StrokeThickness can set multi value

Start by locating the MAUI Border control's StrokeThickness and Frame control's CornerRadius entry points, then compare their current single-value behavior with the WPF and MAUI XAML examples in the issue. Done means Border accepts four-sided StrokeThickness values and Frame accepts four-sided CornerRadius values consistently across supported platforms, with coverage for the new behavior.