Create an option to archive/unarchive Project Groups

Description

There is an ability to archive a project within a group, but there is no ability to archive an entire group with GitLab today.

If a product is mothballed, the operations team would like to archive the GitLab Group (& projects) so that it no longer appears within the GitLab UI like an active product that is under development.

Proposal

Within the Admin Area, add a UI feature for "Archive group" to the "Edit Group" screen in GitLab. When archived, a group will be hidden from the main Group listing (outside of Admin Area) When archived, a group will be visible within the Admin Area only When archived, a group can be unarchived by locating the group within the Admin Area, clicking "Edit Group" and select "unarchive"

Links / references

Found this old request for this feature that appears to have gotten discarded for some reason in 2014: https://github.com/gitlabhq/gitlabhq/issues/7476