rosco 1.6.0

chore(dependencies): Autobump korkVersion/
feat(provider/huaweicloud): Add Huawei Cloud bakery to build VM image.
chore(mergify): Allow OSS approvers to auto-submit.
ix(gce): Remove recently unpublished 'trusty' base image, add 'bionic'.
fix(gce): Remove Trusty GCE image in halconfig/images.yml, add Bionic.
refactor(artifacts): Use builder to create artifacts.
chore(dependencies): Upgrade Spring Boot to 2.2.1.
chore(release): Use buster-slim instead of alpine as the base OS.
fix(release): switch back to Alpine, but don't use the openjdk container.
chore(jobexecutor): log stdout/err for failed bakes to debug integration test failures.
chore(release): update the containers to Alpine 3.11.
chore(dependencies): Reverting Spring Boot 2.2 upgrade.