Merge branch 'control-dropdown-permissions' into 'master'

Hide group control nav if no options present

## What does this MR do?

Hides the group nav controls if no options present in the dropdown.
Also fixed the alignment of the dropdown to match the project page.

## What are the relevant issue numbers?

Closes #19120 

See merge request !5155

app/views/layouts/nav/_group.html.haml

+= render 'layouts/nav/group_settings'
 .scrolling-tabs-container{ class: nav_control_class }
-  = render 'layouts/nav/group_settings'
   .fade-left
     = icon('angle-left')
   .fade-right

app/views/layouts/nav/_group_settings.html.haml

 - if current_user
+  - can_admin_group = can?(current_user, :admin_group, @group)
   - can_edit = can?(current_user, :admin_group, @group)
   - member = @group.members.find_by(user_id: current_user.id)
   - can_leave = member && can?(current_user, :destroy_group_member, member)
 
+  - if can_admin_group || can_edit || can_leave
     .controls
       .dropdown.group-settings-dropdown
         %a.dropdown-new.btn.btn-default#group-settings-button{href: '#', 'data-toggle' => 'dropdown'}
           = icon('cog')
           = icon('caret-down')
         %ul.dropdown-menu.dropdown-menu-align-right
+          - if can_admin_group
             = nav_link(path: 'groups#projects') do
               = link_to 'Projects', projects_group_path(@group), title: 'Projects'
+          - if can_edit || can_leave
             %li.divider
           - if can_edit
             %li