Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Add support for Elasticsearch version 7.3.*

Also update ElasticV7QueryProjectsTest to use V7_3.

Change-Id: Ib7081c5b15756e2ca91d448430928b2f5b8aca50
tree: 65ef51ba1d8213faa657fef8d282a7c9e37c41d1
  1. java/
  2. javatests/