Add Keyboard Navigation To Color Picker (#9144)

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## Summary of the Pull Request

Add the keyboard navigation to the color picker. 
Test manually.

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## References

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## PR Checklist
* [x] Closes #6675
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

Tested manually

src/cascadia/TerminalApp/ColorPickupFlyout.xaml

@@ -12,7 +12,7 @@
         </Style>
     </Flyout.FlyoutPresenterStyle>
     <StackPanel Orientation="Horizontal">
-        <StackPanel>
+        <StackPanel XYFocusKeyboardNavigation="Enabled">
             <VariableSizedWrapGrid Orientation="Horizontal" MaximumRowsOrColumns="4" HorizontalAlignment="Center" Margin="0, 3, 0, 0">
                 <VariableSizedWrapGrid.Resources>
                     <Style TargetType="Rectangle">