Update redirected navbar links

As part of gitlab#30718 (closed), I spent a couple hours today digging through the navbar to make sure we aren't linking to any redirect files. Turns out, we are... in several places. 💦

This covers a lot of housekeeping:

• Updates all the redirected links
• Removes a few navbar items. The removed items were already moved to different places in the navbar, but the old location was never actually removed. (Ignoring analytics pages, which are currently under review separately)
• Fixes the line spacing between sections in the side-project navs to match the main project nav style:
  • Runner had too many line spaces.
  • Charts didn't have enough line spaces.
• Adds a few missing charts docs (only because it was glaringly missing, based on the index page I saw, which linked out to 4 pages that were not in the nav)

Related to gitlab#30718 (closed)