add tool links to gear menus on assignments, quizzes and pages

test plan:
* as with g/39874, add an external tool to a course
with 'assignment_menu', 'quiz_menu' and 'wiki_page_menu'
configured
* enabled lor feature flag for account or user

* confirm that menu items for the tool are added to the
 gear menus on the index and individual show pages for
 assignments, quizzes and page

closes #CNVS-14555 #CNVS-14556 #CNVS-14557 #CNVS-14558 #CNVS-14559 #CNVS-14560

Change-Id: Ib5fcda93b51567bc3e64229014822382918113ac
Reviewed-on: https://gerrit.instructure.com/40168
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>