New navigation display tooltip on keyboard focus

What does this MR do and why?

Tooltip displays for "Stop impersonating" and "Pin/Unpin x" buttons on focus but not for other buttons.

Focus should reveal tooltips so that a user can understand the purpose of UI elements when test isn't available by default. (Also noted in the findings of &11512)

See findings and recordings from new navigation accessibility screen reader review &11510 (closed)

Screenshots or screen recordings

Before	After
CleanShot_2023-10-10_at_12.36.47	CleanShot_2023-10-10_at_12.39.11

How to set up and validate locally

1. tab through new navigation
2. Icon buttons without a label should display a tooltip on :focus and :hover

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 #426362 (closed)