Make Identicon for avatars a shared component

What does this MR do?

This MR makes auto-avatars component GroupIdenticon a shared Vue component and renames it to Identicon

Why was this MR needed?

This MR is a dependency for !13866 (merged).

Does this MR meet the acceptance criteria?

• [ ] Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• [ ] Tests added for this feature/bug
• Review
  • [ ] Has been reviewed by UX
  • Has been reviewed by Frontend
  • [ ] Has been reviewed by Backend
  • [ ] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #35010 (closed)