Webpack auto include for EE imports

What does this MR do?

Webpack currently auto imports scripts found in /pages/ in CE.

This MR auto imports EE scripts found in /ee/.../pages/. If a page has a CE and EE page script, the EE script is loaded instead.

The performance impact of this MR on the webpack compile time is O(n). This impact is negligible. This is because we override the existing entries rather than creating a new mapping based on the differences between CE and EE entries.

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

Make sure everything is 💯

Why was this MR needed?

Enable dynamic imports for EE specific pages

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/41341