Add RPC endpoint to registry to retrieve optimized image ref. (#2114)

* Add RPC endpoint to registry to retrieve optimized image ref.

This RPC is also responsible for validating that the client has access
to the target image.

enterprise/server/registry/BUILD

@@ -13,27 +13,32 @@ go_library(
         "//server/backends/blobstore",
         "//server/config",
         "//server/environment",
+        "//server/http/filters",
         "//server/interfaces",
         "//server/real_environment",
         "//server/remote_cache/cachetools",
         "//server/remote_cache/digest",
         "//server/ssl",
         "//server/util/flagutil",
         "//server/util/grpc_client",
+        "//server/util/grpc_server",
         "//server/util/healthcheck",
         "//server/util/log",
         "//server/util/lru",
         "//server/util/status",
+        "@com_github_google_go_containerregistry//pkg/authn",
         "@com_github_google_go_containerregistry//pkg/name",
         "@com_github_google_go_containerregistry//pkg/v1:pkg",
         "@com_github_google_go_containerregistry//pkg/v1/empty",
+        "@com_github_google_go_containerregistry//pkg/v1/match",
         "@com_github_google_go_containerregistry//pkg/v1/mutate",
         "@com_github_google_go_containerregistry//pkg/v1/partial",
         "@com_github_google_go_containerregistry//pkg/v1/remote",
+        "@com_github_google_go_containerregistry//pkg/v1/remote/transport",
         "@com_github_google_go_containerregistry//pkg/v1/tarball",
         "@com_github_google_go_containerregistry//pkg/v1/types",
-        "@com_github_google_uuid//:uuid",
         "@go_googleapis//google/bytestream:bytestream_go_proto",
+        "@org_golang_google_grpc//:go_default_library",
         "@org_golang_google_protobuf//proto",
         "@org_golang_x_sync//errgroup",
         "@org_golang_x_sync//singleflight",