Resolve "missing design for wiki page"

To Do:

• Move page navigation from sub-menu to sidebar menu
• Update wiki page header
• Update wiki edit page actions and header
• Update Git access page design
• Add search to sidebar navigation

Screen Shots:

@media (min-width: $screen-lg)

@media (min-width: $screen-md)

@media (min-width: $screen-sm)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• 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 it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #18546 (closed)