19164 Add settings dropdown to mobile screens

What does this MR do?

Adds the settings dropdown to mobile screens

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #19164 (closed)

mentioned in issue #19164 (closed)

added ~978334 label

added 1 commit

• 87346bfe - Remove settings cog from within admin scroll tabs; keep links centered

Compare with previous version

added ~149423 label

changed milestone to %8.16

This was merged yesterday

closed

mentioned in issue #27510 (closed)

Picked into 8-16-stable, will go into 8.16.4

Picked https://gitlab.com/gitlab-org/gitlab-ce/commit/577bb4ebe83a2ec7811b240b8023b7ff6ef3bb85 - since there were other 2 merges for the same branch with empty changes

removed ~149423 label

mentioned in commit df1500b3

mentioned in issue #27579 (closed)