Improved the behaviour on the Issuable javascript search elements.

What does this MR do?

Improves the functionality of the search component for the Issues and Merge Request search Input boxes

Are there points in the code the reviewer needs to double check?

None that I know of

Why was this MR needed?

To improve accessibility of the search components

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• [ X] CHANGELOG entry added
• Tests
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

! 21984