Either the Libs/JsonSchemaValidation inside EventLogging should be moved out to a library, or if possible, one of the existing json schema libraries in MediaWiki-Vendor (opis/json-schema or justinrainbow/json-schema) should be used instead.
It seems various of the classes in Libs/JsonSchemaValidation have ancestry back in MediaWiki-extensions-JsonData; if we Librarize this code, we can use Composer to include the classes into both (and MediaWiki-Vendor for WMF production), rather than having duplicate code.
It's unclear if opis/json-schema or justinrainbow/json-schema can replace this code in either case, but at least factoring it out into a library would be a good step in the right direction... See also T293710: Remove opis/json-schema from MW vendor now that it's no longer used, everyone's on justinrainbow/json-schema