metropolis: Lock down visibility rules

This formalizes the package structure introduced by D683.

Test Plan: Pure refactor, CI only.

X-Origin-Diff: phab/D684
GitOrigin-RevId: 574aa14c71faf94f4a5c02a2110e2e3fef7d36ac
diff --git a/metropolis/test/launch/cli/launch-multi2/BUILD.bazel b/metropolis/test/launch/cli/launch-multi2/BUILD.bazel
index 4b51824..aeb19ec 100644
--- a/metropolis/test/launch/cli/launch-multi2/BUILD.bazel
+++ b/metropolis/test/launch/cli/launch-multi2/BUILD.bazel
@@ -26,5 +26,5 @@
         "@com_github_bonzini_qboot//:qboot-bin",
     ],
     embed = [":go_default_library"],
-    visibility = ["//visibility:public"],
+    visibility = ["//:__pkg__"],
 )
diff --git a/metropolis/test/launch/cli/launch/BUILD.bazel b/metropolis/test/launch/cli/launch/BUILD.bazel
index 6b1461d..72c8161 100644
--- a/metropolis/test/launch/cli/launch/BUILD.bazel
+++ b/metropolis/test/launch/cli/launch/BUILD.bazel
@@ -16,5 +16,5 @@
         "//third_party/edk2:firmware",
     ],
     embed = [":go_default_library"],
-    visibility = ["//visibility:public"],
+    visibility = ["//:__pkg__"],
 )