1. We can create the note directly on the issue, rather than attaching
   it after creation.
2. We need to update the MergeRequestClosesIssues relation to ensure
   that the issue know that it's closed by the MR.
3. We should also check that the unavailable button is displayed - not
   just that the available button is displayed.

Cleaned up global namespace JS

Original MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6229

## What does this MR do?
Cleans up javascript global namespace by moving the functions that were previously on the window.doSomething namespace

## Are there points in the code the reviewer needs to double check?
None that I'm aware of

## Why was this MR needed?
Improves code maintainability and deals with some of the technical debt 

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [X] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [X] All builds are passing
- [X] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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)

## What are the relevant issue numbers?
Closes #19661

See merge request !7208

Add tip for using Chrome to run and debug teaspoon tests.

## What does this MR do?

Documents the approach I use when writing and debugging frontend tests, which is (IMHO) much better than running locally from the command line.

See merge request !7257

Ignore `builds` directory from eslint

Running `rake eslint` locally was including this directory reporting so many errors that are not from our source code.

See merge request !7279

Moved most of the functions that contained "window.doSomething" that were located at:
- app/assets/javascripts/application.js
To the following file:
- app/assets/javascripts/lib/utils/common_utils.js

The functions listed here:
- window.ajaxGet
- window.split
- window.extractLast
- window.rstrip
- window.disableButtonIfEmptyField
- window.disableButtonIfAnyEmptyField
- window.sanitize
- window.unbindEvents
- window.shiftWindow

Now will be accessible from the "gl.utils" namespace

eslint: Fix invalid filename validation

Attempt to fix the following error which is appearing in every new MR since `eslint-plugin-filenames` was introduced.

```
/builds/gitlab-org/gitlab-ce/app/assets/javascripts/gl_field_error.js.es6
  2:1  error  Filename 'gl_field_error.js.es6' does not match the naming convention  filenames/match-regex
```

This was happening because our ES6 files have the following structure `gl_hello_world.js.es6`. So `eslint-plugin-filenames` was considering as base name `gl_hello_world.js` which didn't pass the previous regex `^[a-z_]+$`

This new regex allows the following filenames to pass as valid:

- `gl_hello_world.js.es6` which base name translates to `gl_hello_world.js` 
-  `gl_foo_bar.js` which base name translates to `gl_foo_bar`
-  `d3.js` which base name translates to `d3` (especial case, maybe we should move this to the vendor dir and make the regex more specific)

See merge request !7281