Fixes labels multi-encode and selecting labels with single quotes

## What does this MR do?

Replaced single quotes with escaped single quotes when setting item `.is-active` and when removing its field.

Adds a test to test selecting 2 different labels _(one with a single quote)_ with a full page load inbetween, it checks the labels are selected as well as shown as `.is-active` in the list.

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



## Why was this MR needed?

The javascript handles the url encoding when it is sent to the server so we shouldn't let the javascript begin processing an already encoded string but we needed to stop single quotes from breaking a jquery selector.

## Screenshots (if relevant)

https://youtu.be/-H0_L2hV9tM

## Does this MR meet the acceptance criteria?

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

## What are the relevant issue numbers?

Closes #21961

Closes #21880

Closes #21248

Closes #20759

Closes #21935

See merge request !6313