Ability for admins to override the artifacts size per project/group

Description

Currently, the artifacts size is set to 100MB by default in the admin area settings. On GitLab.com we have a limit of 1GB. There might be cases where this limit should be lifted on certain projects.

A real case scenario is our docs site which is deployed on GitLab Pages. We've rolled out versioning, but that increased its size significantly: almost 120MB per version, at the moment around 200MB in total. I see it becoming a problem if we keep piling them up, since we will exceed the limit at some point. We may need to devise a rotation mechanism because of this.

Proposal

Add an option in the group/project settings to override the global artifacts size limit (only admins). Much like we do for the repository size limit.