Issue #2389697 by Wim Leers, Gábor Hojtsy: Editor settings altering not needed (and not compatible with config schema assumptions)
Issue #2390445 by Gábor Hojtsy: System module tests don't pass config schema check
Issue #2248977 by Berdir: Complete support for multi-value base fields in ContentEntitySchemaHandler and use it for the user.roles field