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)
![mobile-safari-fix](/uploads/b38bba735530eb11507fe03036292dd8/mobile-safari-fix.gif)

See merge request !4869