Add delimiter to project stars and forks count

## What does this MR do?
Adds the `number_with_delimiter()`to the project stars and fork counts on the projects dashboard.

## Are there points in the code the reviewer needs to double check?
Shouldn't be any 😃  

## Why was this MR needed?
Improve readability and adhere to the [UI guide](https://gitlab.com/help/development/ui_guide.md#counts)

## What are the relevant issue numbers?
Closes #20746 

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-08-09_at_1.30.44_PM](/uploads/69592ce220d64774e265cfbcfcb6864a/Screen_Shot_2016-08-09_at_1.30.44_PM.png)

After:
![Screen_Shot_2016-08-09_at_1.30.58_PM](/uploads/1470179256614c2e47cc9d0e49aeaf09/Screen_Shot_2016-08-09_at_1.30.58_PM.png)

## 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)

See merge request !5741