Refactor Wikis page bundles

What does this MR do and why?

It breaks down a single JavaScript page bundle used by all Wiki pages into smaller JavaScript page bundles that only contain the functionalities required by a given page. These are the new page bundles and what they contain:

• edit.js contains all the applications used in the Wiki page editor like the WikiForm Vue app, ZenMode, and deleteWikiModal
• async_edit.js loads the edit page bundle asynchronously. This is required because creating and viewing a Wiki page share the same rails route.
• git_access loads the clone panel app.
• diffs load the initDiffStatsDropdown app.

What is the bundle size impact of this change?

This change reduces the bundle size of the Wiki’s read-only pages in 36%!

Screenshots or screen recordings

This MR doesn’t introduce user-facing changes

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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