Wikibase has a small custom CI setup that is fairly outdated now, and we should migrate it to use the standard jobs that nearly all other extensions use.
So we'd drop:
- mwext-Wikibase-repo-tests-sqlite-hhvm-jessie
- mwext-Wikibase-client-tests-mysql-hhvm-jessie
And add quibble equivalent jobs that do the same thing.
This requires being able to load slightly different config into quibble jobs & being able to have extra quibble jobs defined for runs with this extra config.