Fix avatar popover not appearing for delayed data

What does this MR do?

Fix avatar popover not appearing for delayed data

• the popover is added via the CSS class js-user-link to the user link. However, is only done once when the page is loaded, so user links that appear after the page is loaded do not get the popover
• on page update, check for avatar links and add popovers

Screenshots

Before	After
	add_avatar_popover_720p

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #214594 (closed)