Adds diff expansion button to right side of diff

What does this MR do and why?

Adds the diff expansion cell to the right side of the diff when in side-by-side view.

Screenshots or screen recordings

How to set up and validate locally

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

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.

Closes #363278 (closed)