Resolve "Scrolling horz on iOS for the secondary nav is broken"
## What does this MR do?
Moves absolutely positioned `div`s outside of the scrolling container because mobile safari causes those elements to jump around on scroll.
## Are there points in the code the reviewer needs to double check?
Check on a real iPhone (was only able to check in iOS simulator)
## Why was this MR needed?
Mobile Safari.
## What are the relevant issue numbers?
Closes #18438
## Screenshots (if relevant)
See merge request !4869
