Suggest add a Space property to the StackPanel

[mzy666888]

When adding multiple controls to a StackPanel, it is necessary to set a margin for each control and maintain the same interval.

[lindexi]

Reference: https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.stackpanel.spacing?view=winrt-26100

StackPanel.Spacing

Gets or sets a uniform distance (in pixels) between stacked items. It is applied in the direction of the StackPanel's Orientation.

[miloush]

Related #3592, should probably done on all panels at the same time