Clean-up Journey Audiences

From V12.1.7 onwards, journey audiences can be removed from live running journeys. There will be a cron job scheduled (customer can configure cron expression as required), which will find all audiences with status JOURNEY_COMPLETED and JOURNEY_ENDED and will remove those, as well as their related data (like audience responses, milestone, goals, etc data) from respective tables. This removed data will not be recoverable. This will help in improving overall performance of journey engine. To support this feature, introduced properties in engine's file. More information about these properties are added in Journey Administrator's Guide.