Fix DatePicker to respect Width by removing MinWidth from internal Button (#20487)

Co-authored-by: Julien Lebosquain <julien@lebosquain.net>

src/Avalonia.Themes.Fluent/Controls/DatePicker.xaml

@@ -79,6 +79,8 @@
     <Setter Property="CornerRadius" Value="{DynamicResource ControlCornerRadius}" />
     <Setter Property="HorizontalAlignment" Value="Left" />
     <Setter Property="VerticalAlignment" Value="Center" />
+    <Setter Property="MinWidth" Value="{DynamicResource DatePickerThemeMinWidth}" />
+    <Setter Property="MaxWidth" Value="{DynamicResource DatePickerThemeMaxWidth}" />
     <Setter Property="Template">
       <ControlTemplate>
         <DataValidationErrors>
@@ -91,8 +93,7 @@
                     BorderThickness="{TemplateBinding BorderThickness}"
                     CornerRadius="{TemplateBinding CornerRadius}"
                     IsEnabled="{TemplateBinding IsEnabled}"
-                    MinWidth="{DynamicResource DatePickerThemeMinWidth}"
+                    MaxWidth="{TemplateBinding MaxWidth}"
-                    MaxWidth="{DynamicResource DatePickerThemeMaxWidth}"
                     HorizontalAlignment="Stretch"
                     VerticalAlignment="Stretch"
                     TemplatedControl.IsTemplateFocusTarget="True">