Changes

* Continued work on telemetry* Uplifting final reading list migration bugs, including support for [https://bugzilla.mozilla.org/show_bug.cgi?id=1269734 Adjust campaign id]* Working on [https://bugzilla.mozilla.org/show_bug.cgi?id=1274029 performance regression introduced by new top sites query]* JanH working on moving the [https://bugzilla.mozilla.org/show_bug.cgi?id=1251362 recent tabs panel into history]* Enabling Disabling most [https://github.com/mozilla-services/switchboard-experiments/blob/master/experiments.json experiments], but enabling "Add to homescreen" prompt up to beta* Helping Taipei team with [https://bugzilla.mozilla.org/show_bug.cgi?id=1240423 media control notification]