Limit build visibility of modules in apex/...

This changes the default visibility of soong modules in this directory
to __subpackages__, from the current public default.

This helps accidental dependencies sneaking in without intent from
the module owner.

Bug: 175604587
Test: m nothing
Change-Id: I1df8b8e087d27f62ce8c09d7e6e32d511efdba6b
diff --git a/apex/blobstore/service/Android.bp b/apex/blobstore/service/Android.bp
index 22b0cbe..f6cbac1 100644
--- a/apex/blobstore/service/Android.bp
+++ b/apex/blobstore/service/Android.bp
@@ -25,4 +25,9 @@
         "services.core",
         "services.usage",
     ],
+    visibility: [
+        // These are required until blobstore is properly unbundled.
+        "//frameworks/base/services",
+        "//frameworks/base/services/tests/mockingservicestests",
+    ],
 }