[Functionbeat] Kinesis timestamp ignored

[adrian-skybaker]

Similar to #12412, the kinesis source ignores the timestamp in the record and uses time.Now():

		for _, deaggRecord := range deaggRecords {
			beatEvents = append(beatEvents, beat.Event{
				Timestamp: time.Now(),

This is at odds with the documentation at https://www.elastic.co/guide/en/beats/functionbeat/current/exported-fields-ecs.html:

@timestamp
Date/time when the event originated. This is the date/time extracted from the event, typically representing when the event was generated by the source. If the event source has no original timestamp, this value is typically populated by the first time the event was received by the pipeline.