Separate cohorts logic from users controller. But keep cohorts as a tab
under admin/users page.
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Changelog: changed
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

This changes the tabs in the admin user list to do a full page reload so
that we load data only for the active tab.

Changelog: performance

Cohorts information is available
in users page of adminarea

Remove analytics icon from top nav bar
Move Cohorts and DevOps Score pages to Admin panel
under Analytics submenu
Keep old paths but redirect to new pages under /admin
Make sure that Cohorts and DevOps Score are
visible only to Admin, remove a toggle that
was enabling instance statistics to be seen
by not admin user
Ignore instance_statistics_visibility_private
column as the first step to drop it,
remove obsolete condition from global policy
and ignored application setting