Group Setting: Add toggle to remove Issues left nav item
Problem to solve
In a group, no left sidebar menus can be turned off, but they can for projects. However, there are a number of use cases where a GitLab group may be used and the GitLab features in the sidebar aren't relevant.
Proposal
We should allow users to toggle off the Issues left nav item in Group Settings.
Consideration: Should we allow this if sub-groups or projects have the issue tracker enabled?
Documentation
We will need to update our documentation on group settings.