Convert some vendored javascript assets to npm modules

What does this MR do?

• Remvoes vue.js from /vendor/assets/javascripts/ because it is now being included via node_modules.
• Replaces timeago.js in vendor directory with npm module
• Replaces js.cookie in vendor directory with npm module

Are there points in the code the reviewer needs to double check?

Make sure everything compiles correctly and passes CI. The version number for timeago.js and js.cookie may have been bumped in the process, so make sure these still work as expected. (minor semver bump shouldn't have breaking changes, so probably not a problem)

Why was this MR needed?

Part of an ongoing effort to drain /vendor/assets/javascripts in favor of package.json controlled dependencies.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry 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?

#27486 (moved)