Merge branch 'master' into stable-5.4

* master:
  ReachabilityCheckers: @since 5.4
  Update Orbit to S20190521195709 for 2019-06 M3
  Tune max heap size for tests
  GPG: check that the key found is a signing key
  GPG: use key fingerprint suffix to compare id for signing key
  Recognize ReachabilityCheckerTestCase as helper
  UploadPack: restore inadvertently deleted line
  UploadPack: Use reachability checker to validate non-advertised wants
  Bazel: Simplify names of bouncy castle libraries
  Convert to lambda or member reference
  BitmappedReachabilityChecker: Reachability check using bitmaps
  BitmapCalculator: Get the reachability bitmap of a commit
  ReachabilityChecker: Default implementation with a RevWalk

Change-Id: I323c460853230abcffa94c4f34f15dbaff8c330c