Ability to enforce Repository size limit: second iteration

Description

In 8.12 we added the ability to enforce Repository size limit (https://gitlab.com/gitlab-org/gitlab-ee/issues/559).

We now need to display a banner at the top of the project when it's over limit, saying the project is over limit.

Wireframes

References

• First iteration: https://gitlab.com/gitlab-org/gitlab-ee/issues/559