Move avatars in avatar-group into a slot #4291
Description
Describe your motivation
For consistency with other components containing multiple items, especially ones represented by nested web components, which would also make ::part() based styling possible without exportparts, and without exposing the avatars' focus, focus-ring and expanded states as additional part values.
Describe the solution you'd like
Introduce a slot in vaadin-avatar-group and refactor the avatars to be in it instead of in shadow dom.
Describe alternatives you've considered
No response
Additional context
No response