Create shared user-avatar-list component

What does this MR do?

This MR creates a user-avatar-list component which is needed by gitlab-ee!9003.

Screenshots

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What are the relevant issue numbers?

• Part of gitlab-ee#1979
• FE gitlab-ee#8350

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer