Clean up coffeescript files imported from GitLab CI

## What does this MR do?

This MR cleans up CoffeeScript files imported from GitLab CI along with a strategy #19159. Some files should have been removed in !1987.

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

While I think the `Build` module should be named as `Build`, not `CiBuild` in the JavaScript namespace, please check if it should.

## Why was this MR needed?

Removing unused coffeescript files reduces time to build JS and so time to transfer even in production. The fewer files, the better, too.

## What are the relevant issue numbers?

Closes #19159

## Screenshots (if relevant)

n/a

## Does this MR meet the acceptance criteria?

- [skipped] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [skipped] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [skipped] API support added
- Tests
  - [skipped] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4925