CommandBar's overflow menu doesn't work with keyboard #21000
Description
Describe the bug
The command bar items in the overflow of a CommandBar are not navigable with the keyboard.
To Reproduce
Click on the overflow menu of a CommandBar. Try to use the Up/Down arrow keys: the selection does not move.
Expected behavior
The overflow menu should be behaving the same as a standard menu.
Avalonia version
12.0.0-rc2, master
OS
No response
Additional context
The overflow menu is currently a simple ItemsControl. A menu should probably be used instead, to get all those features for free.