Add proper support for TextBox.InnerLeftContent with watermarks and labels

[SKProCH]

Discussed in #279

^{Originally posted by CastelloBrancoTecnologia August 14, 2023}

inestead of this

in

<TextBox ..... >
<TextBox.InnerLeftContent>
<icons:MaterialIcon
Width="24"
Height="24"
Margin="4"
HorizontalAlignment="Left"
VerticalAlignment="Bottom"
Foreground="{DynamicResource PrimaryHueMidBrush}"
Kind="KeyVariant" />
</TextBox.InnerLeftContent>

[cesarchefinho]

I think this is not an enhancement, but a BUG a floting label/whatermark colide with Left content part