Merge branch 'stable-2.16' into stable-3.0

* stable-2.16:
  Error Prone: Enable DateFormatConstant at ERROR severity
  Synchronize protobuf with version used in rules_closure
  Update rules_closure to latest version
  Upgrade elasticsearch-rest-client to 7.1.1

Change-Id: I00004567e675b67f498a2edfb93951a5aab140f5
tree: 1a7afd3e3cd4126f07c45b6aff41a7a1afa5c96f
  1. java/
  2. javatests/