Add default_visibility for soong modules

So that we don't get surprise usages.

Bug: 348717861
Test: m nothing
Change-Id: I47319a727092c1bd936cca88f5713ee977a48b48

java/Android.bp

@@ -120,4 +120,5 @@ bootstrap_go_package {
         "test_spec_test.go",
     ],
     pluginFor: ["soong_build"],
+    visibility: ["//visibility:public"],
 }

java/config/Android.bp

@@ -17,4 +17,8 @@ bootstrap_go_package {
         "kotlin.go",
         "makevars.go",
     ],
+    visibility: [
+        "//build/soong:__subpackages__",
+        "//external/error_prone/soong",
+    ],
 }

java/metalava/Android.bp

@@ -15,4 +15,5 @@
 filegroup {
     name: "metalava-config-files",
     srcs: ["*-config.xml"],
+    visibility: ["//visibility:public"],
 }