This updates to Ember 3.16 but leaves Ember Data at 3.12 so we don’t need
to use the model fragments beta. It can be reviewed on a commit-by-commit
basis: blueprint updates, fixes for test failures, and the removal of
now-deprecated partials.
It’s not a true update to Octane as that would involve turning on template-only
components by default, which breaks various things. We can accomplish that
separately and then add the edition setting to package.json.
This surfaces test failures more clearly on CircleCI by adding
testem-multi-reporter to report both via the default TAP reporter
as well as an xUnit reporter whose output is stored as an artefact.
