Add Pending Tab to Builds
## What does this MR do?
Add Pending Tab to Builds and separate "running" and "pending" jobs in UI.
## Why was this MR needed?
Increase visibility to "pending" .
## What are the relevant issue numbers?
Closes#19408
## Screenshots
Before:
After:
## 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 [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)
cc @ubudzisz @yorickpeterse @grzesiek @tmaczukin @zj [@chastell](https://github.com/chastell) [@tomash](https://github.com/tomash)
See merge request !5084
08e21230b1