WIP Add client side grpc logging for gitaly-ruby

Part of gitlab-com/gl-infra/scalability#519 (closed)

Example output:

{
  "correlation_id":"b8326716-4138-48ce-9ee7-3289f7ea4485",
  "grpc.code":"OK",
  "grpc.meta.auth_version":"v2",
  "grpc.meta.client_name":"gitlab-web",
  "grpc.meta.deadline_type":"regular",
  "grpc.method":"GetNewLFSPointers",
  "grpc.request.deadline":"2020-10-14T17:42:50+02:00",
  "grpc.request.fullMethod":"/gitaly.BlobService/GetNewLFSPointers",
  "grpc.request.glProjectPath":"root/test-pages-2",
  "grpc.request.glRepository":"project-20",
  "grpc.request.repoPath":"@hashed/f5/ca/f5ca38f748a1d6eaf726b8a42fb575c3c71f1864a8143301782de13da2d9202b.git",
  "grpc.request.repoStorage":"praefect-internal-0",
  "grpc.request.topLevelGroup":"@hashed",
  "grpc.service":"gitaly.BlobService",
  "grpc.start_time":"2020-10-14T17:42:20+02:00",
  "grpc.time_ms":0.057,
  "level":"info",
  "msg":"finished client streaming call",
  "peer.address":"",
  "pid":84974,
  "span.kind":"client",
  "system":"grpc",
  "time":"2020-10-14T17:42:20.682Z",
  "type":"gitaly-ruby"
}
{
  "correlation_id":"SjbndjbyPs6",
  "grpc.code":"OK",
  "grpc.meta.auth_version":"v2",
  "grpc.meta.client_name":"gitlab-web",
  "grpc.meta.deadline_type":"regular",
  "grpc.method":"UserCreateTag",
  "grpc.request.deadline":"2020-10-14T17:43:15+02:00",
  "grpc.request.fullMethod":"/gitaly.OperationService/UserCreateTag",
  "grpc.request.glProjectPath":"root/test-pages-2",
  "grpc.request.glRepository":"project-20",
  "grpc.request.repoPath":"@hashed/f5/ca/f5ca38f748a1d6eaf726b8a42fb575c3c71f1864a8143301782de13da2d9202b.git",
  "grpc.request.repoStorage":"praefect-internal-0",
  "grpc.request.topLevelGroup":"@hashed",
  "grpc.service":"gitaly.OperationService",
  "grpc.start_time":"2020-10-14T17:42:20+02:00",
  "grpc.time_ms":974.002,
  "level":"info",
  "msg":"finished client unary call",
  "peer.address":"",
  "pid":84974,
  "span.kind":"client",
  "system":"grpc",
  "time":"2020-10-14T17:42:21.217Z",
  "type":"gitaly-ruby"
}