TabBarItemView's root view is zero-sized making it hard to use in stack views

[MathieuKavalec]

Environment Information

• Platform:
  • iOS
  • macOS

Please provide a reproduction of the bug:

Add TabBarItemViews to a stack view. Set the content hugging priority to minimize the size of the views.

Actual behavior:

Notice that the views get squished.
Through the view hierarchy debugger, we can see that the TabBarItemView's root view is zero-sized.
The label and image that are contained in that view are displayed outside of their root view's bounds.

Expected behavior:

TabBarItemView should contain its subviews and have a reliable intrinsic size that reflects its contents.

Priorities and help requested:

Requested priority: Normal