Add browsertime-benchmark-jetstream3 to the android-em-14-arm64 test set at tier 3, and schedule it on autoland for fenix, matching what speedometer3 already does on that platform. Jetstream3 produces many more alerts than speedometer3(none since we landed the sp3 emulator change) so it makes sense to use this benchmark in addition to sp3 because of its ability to show long term trends for alerting. Also raise that emulator's RAM from 3GB to 6GB, which was the culprit behind the jetstream3 job permafailing previously. Differential Revision: https://phabricator.services.mozilla.com/D324733