Change airbnb eslint config package to `eslint-config-airbnb-base` and update plugins.
Change `airbnb` to `airbnb-base` for .eslintrc `extends` value.
Added changelog entry
Made sure all plugins and envs are set
Corrected new failing specs
Replace static fixture for zen_mode_spec
## What does this MR do?
Replace `zen_mode.html.haml` for `zen_mode_spec.js` by already existing dynamically generated fixture.
## What are the relevant issue numbers?
#24753
See merge request !7686
Create dynamic fixture for build_spec
## What does this MR do?
Replace `spec/javascripts/fixtures/build.html.haml` by a dynamically created fixture (using `rake teaspoon:fixtures`).
## Why was this MR needed?
The existing fixture was not representing the real page.
## What are the relevant issue numbers?
#24614 would have been avoided
following !6059
See merge request !7589
Resolve "Activity entries are not loaded fully to cover full window's height"
## What does this MR do?
Fixes a bug in which a browser window large enough to encompass the default number of items in an auto-loading endless-scroll list could not trigger the loading of additional items.
## Are there points in the code the reviewer needs to double check?
I refactored activities.js and pager.js into es6 syntax while I was investigating the issue. No changes were made other than some es6 flourishes and eslint conformity, so nothing should be effected, but perhaps best to double check other pages which utilize these scripts.
## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?
- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) 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 it does - 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#24499
See merge request !7608
Resolve "Display "folders" for environments"
## What does this MR do?
Adds the ability to show the grouped environments inside "folders".
Adds several reusable vue components in order to accomplish the recursive tree data structure presented.
For the individual components, Jasmine tests were added.
For the ones that depend of an API response, rspec tests are used.
## Screenshots (if relevant)




## Does this MR meet the acceptance criteria?
- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
- [x] Added for this feature/bug
- [ ] 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 it does - 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#22539
See merge request !7015
* master: (154 commits)
Fix typos
Fix wrong changelog item
Add missing item for 8.13.6
Change last_used_at to use touch
Add chat_name partial
Mention Git strategy none
Fix code review
adds fix for security issue when annonymous user does not ...
Remove ToC since it's now supported in the docs portal itself
Add 8.14 to versions with further additions to review apps
Add Limitations sections to environments and review apps docs
Add link to environments docs
Fix URL to review apps docs
Add a prerequisites section, add some links
Link to NGINX example project for the time being
Get rid most of the irrelevant sections
Add note about current limitation in $CI_BUILD_REF_NAME
Add an intro and an Overview section for Review Apps
WIP review apps
Add Review apps link to CI README
...
Conflicts:
spec/features/environments_spec.rb