Moved builds panel to the bottom of the builds sidemenu (and change retry link colour)

## What does this MR do?

Moves the builds panel to the bottom of the builds sidemenu.

Changes the `Retry` link to look more _linky_. 🖇  

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

## Why was this MR needed?

On small screens, the builds panel must be scrolled through before you can get to the details of the build you're looking at.

## What are the relevant issue numbers?

Closes #21122

## Screenshots (if relevant)

![Screen_Shot_2016-08-20_at_17.41.51](/uploads/84f10c43011da514ef8ac1b1d20eb5d5/Screen_Shot_2016-08-20_at_17.41.51.png)

## 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 [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)
Closes #21122

See merge request !5923