Group level Container Registry browser
### Problem to solve
The GitLab Container Registry does not provide users the ability to view and pull images at the Group level. As a result, organizations that leverage groups/sub-groups are forced to navigate to individual projects to find the image they are looking for. This results in duplication of efforts or a lack of collaboration on sharing and promoting Docker images amongst teams.
### Proposal
Similar to the GitLab Maven Repository, we will allow users to view and pull Docker images/tags at the group level. Users will still build and push images to a given project, but the images will be available for viewing and pulling at the group level.
In the UI, we will add `Group -> Packages -> Container Registry` below `Group -> Packages -> List` so that users can search, copy image/tag URLs and remove tags.
### Further details
#### User interface
##### Screen capture

##### Screen shots



### Intended users
- [Software Developer](https://design.gitlab.com/research/personas#persona-sasha)
- [DevOps Engineer](https://design.gitlab.com/research/personas#persona-devon)
### Further details
<!-- Include use cases, benefits, and/or goals (contributes to our vision?) -->
### Permissions and Security
- There are no permissions changes needed for this issue.
### Documentation
- There are no documentation changes needed for this issue.
### What does success look like, and how can we measure that?
- Success looks like we see increased usage and adoption of the container registry UI. To start we will use page views as a basic metric.
### Links / references
/label gitlab-ce~10230929
issue