Context switcher doc updates

Based on this issue: #409522 (closed)

Last MR to merge before we update the docs: !129843 (merged)

We will need to update the documentation. This issue is to track that work.

• Need to open MR for style guide.
• Need to open MRs to update docs.
• Don't forget this page, which has lots of changes: https://docs.gitlab.com/ee/user/search/