[New Control] Descriptions (#791)

* feat: add ColumnWrapPanel.

* feat: add Descriptions and DescriptionsItem controls

* WIP: extract a LabeledContentControl for this particular need.

* wip.

* feat: setup demo. fix various initial status issue.

* fix: fix a layout issue.

* feat: improve demo.

* feat: update demo.

* fix: remove a redundant calculation.

* feat: update per copilot feedback.

* feat: add tests, fix a calculation issue.

* feat: refactor to change the default label and value binding assignment logic.

* feat: introduce orientation.

* misc: format codes.

* feat: clarify LabelPosition property.

* feat: extract Font resources.

* revert AvatarDemo.

* feat: assign specific value to Font resources for testing.

* misc: resolve copilot comment.

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Co-authored-by: Zhang Dian <54255897+zdpcdt@users.noreply.github.com>

demo/Ursa.Demo/ViewModels/MainViewViewModel.cs

@@ -47,6 +47,7 @@ public partial class MainViewViewModel : ViewModelBase
             MenuKeys.MenuKeyDatePicker => new DatePickerDemoViewModel(),
             MenuKeys.MenuKeyDateRangePicker => new DateRangePickerDemoViewModel(),
             MenuKeys.MenuKeyDateTimePicker => new DateTimePickerDemoViewModel(),
+            MenuKeys.MenuKeyDescriptions => new DescriptionsDemoViewModel(),
             MenuKeys.MenuKeyDialog => new DialogDemoViewModel(),
             MenuKeys.MenuKeyDisableContainer => new DisableContainerDemoViewModel(),
             MenuKeys.MenuKeyDivider => new DividerDemoViewModel(),