Fix color animation bug of title bar buttons (microsoft#8649)

In dark mode (and high contrast mode), color animation of title bar
button uses wrong color.  Cause of this issue is using invalid data in
`ColorAnimation`.  I fixed this bug by changing `ColorAnimation` value
in XAML layout file.

According to a [forum post], `To` value of `ColorAnimation` must be
frozen. But original source code uses "color binding" which makes this
value dynamic.  As a result, the value set by default is always used,
that means, light mode.

So I added new resource named `CaptionButtonStrokeColor` and
`CaptionButtonBackgroundColor` which has static color value.

In light mode and dark mode, I set `SystemBaseHighColor` in the color
resource.  `SystemBaseHighColor` is the same as
`SystemControlForegroundBaseHighBrush.Color` which is originally used in
animation.

The background color animation happened to work correctly because its
value is the same between light mode and dark mode.  But I also fixed
background color animation.

## Validation Steps Performed

There is no need to add new test with this fix.

- I changed the `theme` value in `settings.json` and confirmed that the
  correct color values were used.
- I confirmed that it works correctly even if the Windows theme is
  changed.

[forum post]: https://social.msdn.microsoft.com/Forums/vstudio/en-US/027c364f-5d75-424f-aafd-7fb76b10b676/templatebinding-on-storyboard?forum=wpf

Closes microsoft#7314

src/cascadia/TerminalApp/MinMaxCloseControl.xaml

@@ -22,9 +22,11 @@ the MIT License. See LICENSE in the project root for license information. -->
                     <StaticResource x:Key="CaptionButtonBackgroundPointerOver" ResourceKey="SystemControlBackgroundBaseLowBrush"/>
                     <StaticResource x:Key="CaptionButtonBackgroundPressed" ResourceKey="SystemControlBackgroundBaseMediumLowBrush"/>
                     <StaticResource x:Key="CaptionButtonStroke" ResourceKey="SystemControlForegroundBaseHighBrush"/>
+                    <StaticResource x:Key="CaptionButtonStrokeColor" ResourceKey="SystemBaseHighColor"/>
                     <StaticResource x:Key="CaptionButtonStrokePointerOver" ResourceKey="SystemControlForegroundBaseHighBrush"/>
                     <StaticResource x:Key="CaptionButtonStrokePressed" ResourceKey="SystemControlForegroundBaseHighBrush"/>
                     <SolidColorBrush x:Key="CaptionButtonBackground" Color="Transparent" />
+                    <Color x:Key="CaptionButtonBackgroundColor">Transparent</Color>
                     <SolidColorBrush x:Key="CloseButtonBackgroundPointerOver" Color="#e81123"/>
                     <SolidColorBrush x:Key="CloseButtonStrokePointerOver" Color="White"/>
                     <SolidColorBrush x:Key="CloseButtonBackgroundPressed" Color="#f1707a"/>
@@ -35,9 +37,11 @@ the MIT License. See LICENSE in the project root for license information. -->
                     <StaticResource x:Key="CaptionButtonBackgroundPointerOver" ResourceKey="SystemControlBackgroundBaseLowBrush"/>
                     <StaticResource x:Key="CaptionButtonBackgroundPressed" ResourceKey="SystemControlBackgroundBaseMediumLowBrush"/>
                     <StaticResource x:Key="CaptionButtonStroke" ResourceKey="SystemControlForegroundBaseHighBrush"/>
+                    <StaticResource x:Key="CaptionButtonStrokeColor" ResourceKey="SystemBaseHighColor"/>
                     <StaticResource x:Key="CaptionButtonStrokePointerOver" ResourceKey="SystemControlForegroundBaseHighBrush"/>
                     <StaticResource x:Key="CaptionButtonStrokePressed" ResourceKey="SystemControlForegroundBaseHighBrush"/>
                     <SolidColorBrush x:Key="CaptionButtonBackground" Color="Transparent" />
+                    <Color x:Key="CaptionButtonBackgroundColor">Transparent</Color>
                     <SolidColorBrush x:Key="CloseButtonBackgroundPointerOver" Color="#e81123"/>
                     <SolidColorBrush x:Key="CloseButtonStrokePointerOver" Color="White"/>
                     <SolidColorBrush x:Key="CloseButtonBackgroundPressed" Color="#f1707a"/>
@@ -46,9 +50,11 @@ the MIT License. See LICENSE in the project root for license information. -->
                 <ResourceDictionary x:Key="HighContrast">
                     <x:Double x:Key="CaptionButtonStrokeWidth">3.0</x:Double>
                     <SolidColorBrush x:Key="CaptionButtonBackground" Color="{ThemeResource SystemColorButtonFaceColor}"/>
+                    <StaticResource x:Key="CaptionButtonBackgroundColor" ResourceKey="SystemColorButtonFaceColor"/>
                     <SolidColorBrush x:Key="CaptionButtonBackgroundPointerOver" Color="{ThemeResource SystemColorHighlightColor}"/>
                     <SolidColorBrush x:Key="CaptionButtonBackgroundPressed" Color="{ThemeResource SystemColorHighlightColor}"/>
                     <SolidColorBrush x:Key="CaptionButtonStroke" Color="{ThemeResource SystemColorButtonTextColor}"/>
+                    <StaticResource x:Key="CaptionButtonStrokeColor" ResourceKey="SystemColorButtonTextColor"/>
                     <SolidColorBrush x:Key="CaptionButtonStrokePointerOver" Color="{ThemeResource SystemColorHighlightTextColor}"/>
                     <SolidColorBrush x:Key="CaptionButtonStrokePressed" Color="{ThemeResource SystemColorHighlightTextColor}"/>
                     <SolidColorBrush x:Key="CloseButtonBackgroundPointerOver" Color="{ThemeResource SystemColorHighlightColor}"/>
@@ -95,8 +101,8 @@ the MIT License. See LICENSE in the project root for license information. -->
                                         <VisualStateGroup.Transitions>
                                             <VisualTransition From="PointerOver" To="Normal">
                                                 <Storyboard>
-                                                    <ColorAnimation Storyboard.TargetName="ButtonBaseElement" Storyboard.TargetProperty="(UIElement.Background).(SolidColorBrush.Color)" To="{Binding Color, Source={ThemeResource CaptionButtonBackground}}" Duration="0:0:0.2"/>
-                                                    <ColorAnimation Storyboard.TargetName="Path" Storyboard.TargetProperty="(UIElement.Stroke).(SolidColorBrush.Color)" To="{Binding Color, Source={ThemeResource CaptionButtonStroke}}" Duration="0:0:0.1"/>
+                                                    <ColorAnimation Storyboard.TargetName="ButtonBaseElement" Storyboard.TargetProperty="(UIElement.Background).(SolidColorBrush.Color)" To="{ThemeResource CaptionButtonBackgroundColor}" Duration="0:0:0.2"/>
+                                                    <ColorAnimation Storyboard.TargetName="Path" Storyboard.TargetProperty="(UIElement.Stroke).(SolidColorBrush.Color)" To="{ThemeResource CaptionButtonStrokeColor}" Duration="0:0:0.1"/>
                                                 </Storyboard>
                                             </VisualTransition>
                                         </VisualStateGroup.Transitions>