implement 'hidden_in_prod' feature status

this is 'hidden' in production environments and 'allowed' elsewhere

test plan:
 - The 'better_file_browsing' feature should be hidden in production
   environments (such as a portal with config/testcluster.yml
   removed).

fixes CNVS-16352

Change-Id: Ic8eefcb53122d27fbf9094cbc010efdbd40e2a59
Reviewed-on: https://gerrit.instructure.com/43098
Reviewed-by: Jon Willesen <jonw@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cosme Salazar <cosme@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>