Merge branch 'stable-2.15'

* stable-2.15:
  bazlets: Replace native.git_repository with skylark rule
  Upgrade mockito to 2.23.0
  Upgrade bazlets to latest stable-2.15 to build with 2.15.5 API
  Upgrade bazlets to latest stable-2.14 to build with 2.14.15 API
  Update bazlets to latest stable-2.15 to build with 2.15.4 API

Change-Id: Id2441ce1bb0b3ef0a6fe1c2bd155ced8218e0a32