Feature description: getInstalledRelatedApps

Eng owner: ??? 
Product owner: nattestad@

Doc: https://docs.google.com/document/d/135IYDrrp86V26E74GwgSoN6Bdm0sZuRIbi0iHRuFKNA/edit#

This is a tracking bug for turning on an origin trial on for getInstalledRelatedApps. 

Currently needs a champion to be assigned by Peter@chromium.org