Global Search vertical navigation search helper

What does this MR do and why?

this is a fix for this MR that has been merged and reverted due to FOSS being broken

1/5 Provide JSON data for Vue frontend vertical navigation

• Search Page vertical navigation search helper (merged) 👈 this MR
• Search Page layout changes (merged)
• Move filters into their own component (merged)
• Fix search helper vertical navigation JSON method (merged)
• Search Page Vue vertical navigation (merged)
  • Fix missing feature flag check in Vue vertical menu (merged)
  • Convert all Search Page RSpecs to support vertical search navigation

Screenshots or screen recordings

This is backend MR there is no visual change

How to set up and validate locally

1. Checkout this branch
2. In rails console enable a feature flag

   Feature.enable(:search_page_vertical_nav)

3. execute or render

   search_navigation_json

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 to #293740 (closed)