Problem/motivation
Patches at #1648930: Introduce configuration schema and use for translation included full locale integration but that was postponed on other attempts and #1866610: Introduce Kwalify-inspired schema format for configuration got committed after all. So we need to resurrect all the locale / multilingual integration from #1648930: Introduce configuration schema and use for translation (and some that was removed in progress on the kwalify-inspired issue too) to get a fully working integrated system for shipped configuration translation.
Proposed solution
Take things removed in progress in #1866610: Introduce Kwalify-inspired schema format for configuration and the feature set delta between that and #1648930: Introduce configuration schema and use for translation and make it work with the committed metadata system.