[Infra] Replace MetricsUIAggregation in favor of estypes.AggregationsAggregate#190495

jennypavlova merged 18 commits intoelastic:mainelastic/kibana:mainfrom

jennypavlova:190311-infra-replace-metricsuiaggregation-in-favor-of-estypesaggregationsaggregatejennypavlova/kibana:190311-infra-replace-metricsuiaggregation-in-favor-of-estypesaggregationsaggregateCopy head branch name to clipboard