Right now we are using entitySources and the entitySource services in production.
However we currently give Wikibase the legacy configuration, and it munges this into the entitySources configuration.
We should instead directly write the entitySources config, this will allow us to remove the back compat in time.
Steps:
- T248656: entitysources: Directly create entitySources config for beta cluster sites
- T248664: entitysources: Directly create entitySources config for WMF "test" wikis
- T254315: entitysources: Directly create entitySources config for WMF production wikis
Deployment checking code helpers https://phabricator.wikimedia.org/P10913