Transition GitLab pages to object storage instead of NFS
## Note
**Please leave any feedback related to migration on https://gitlab.com/gitlab-org/gitlab/-/issues/331699**
### Problem to Solve
Removing dependency on NFS is part of a [larger technical initiative](https://gitlab.com/groups/gitlab-org/-/epics/1316) to [decrease complexity of the Pages codebase and improve long term scalability](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/58796).
We need to be able to support GitLab pages deployment on Kubernetes as described in [gitlab#39586](https://gitlab.com/gitlab-org/gitlab/-/issues/39586). As currently implemented:
1. Pages does not work when Gitlab is installed using Kubernetes which [impacts customers](https://gitlab.com/gitlab-com/cs-product-feedback/-/issues/5)
2. Pages dependency on NFS impedes the progress of multiple internal initiatives
* Pages must be configurable as part of the Helm Chart Install [https://gitlab.com/gitlab-com/account-management/emea/aldi-sued/collaboration-project/-/issues/48](https://gitlab.com/gitlab-com/account-management/emea/aldi-sued/collaboration-project/-/issues/48)
* NFS Migration effort for GitLab.com [https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/112](https://gitlab.com/groups/gitlab-com/gl-infra/-/epics/112)
* Geo: Support GitLab Pages [https://gitlab.com/groups/gitlab-org/-/epics/589](https://gitlab.com/groups/gitlab-org/-/epics/589)
### Current Status (2021-05-25)
* NFS is fully disabled on gitlab.com
* [self-managed customers can start using new architecture](https://docs.gitlab.com/ee/administration/pages/#migrate-gitlab-pages-to-140)
* we actively work on [deprecations for %"14.0"](https://gitlab.com/groups/gitlab-org/-/epics/3911), starting from it all self-managed customers will automatically switch to new architecture
epic