Show user popover for discussion note avatar

What does this MR do and why?

Note: This MR is a part of a series of MRs where we're making popover behaviour consistent across GitLab.

Shows user popover when hovered over a discussion note avatar across Issues, MRs, Epics, and Work Item.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
Screen_Recording_2023-06-23_at_5.18.23_PM	Screen_Recording_2023-06-23_at_5.15.20_PM

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Go to any Issue, MR, Epic, or a Work Item and view discussion notes, hover over the avatar as shown in the screen recording to open popover.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related Issue

#416174 (closed)