91c4e4c780
This patch adds a lull-schedule attribute to some browsertime live-site tasks so that we can start testing lull-scheduling. The lull-schedule attribute will be used to denote how frequently a particular task should run. The lull-schedule attribute exists first as a raptor specific setting, and is then added to the `extra` section so that we can make use of it in the `mozci` module. Differential Revision: https://phabricator.services.mozilla.com/D212202