metropolis/test/util: move in NewEphemeralClusterCredentials from rpc

Change-Id: I41603b19a76ea91c2191b0118183957973fc9ccd
Reviewed-on: https://review.monogon.dev/c/monogon/+/1960
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/node/core/rpc/BUILD.bazel b/metropolis/node/core/rpc/BUILD.bazel
index c530a65..e1017d7 100644
--- a/metropolis/node/core/rpc/BUILD.bazel
+++ b/metropolis/node/core/rpc/BUILD.bazel
@@ -8,7 +8,6 @@
         "peerinfo.go",
         "server.go",
         "server_authentication.go",
-        "testhelpers.go",
         "trace.go",
     ],
     importpath = "source.monogon.dev/metropolis/node/core/rpc",
@@ -43,6 +42,7 @@
         "//metropolis/pkg/logtree",
         "//metropolis/proto/api",
         "//metropolis/proto/ext",
+        "//metropolis/test/util",
         "@org_golang_google_grpc//:go_default_library",
         "@org_golang_google_grpc//codes",
         "@org_golang_google_grpc//status",