Add default_visibility for soong modules

So that we don't get surprise usages.

Bug: 348717861
Test: m nothing
Change-Id: I47319a727092c1bd936cca88f5713ee977a48b48
diff --git a/compliance/project_metadata_proto/Android.bp b/compliance/project_metadata_proto/Android.bp
index 56e76e7..0c807b2 100644
--- a/compliance/project_metadata_proto/Android.bp
+++ b/compliance/project_metadata_proto/Android.bp
@@ -24,4 +24,5 @@
         "golang-protobuf-reflect-protoreflect",
         "golang-protobuf-runtime-protoimpl",
     ],
+    visibility: ["//build/make/tools/compliance:__subpackages__"],
 }