Make essential Bazel packages publicly visible

This allows separate Bazel projects to reference Nomulus as an external
repository. They can then copy the []
directory structure into their own project and customize the Action
and Module lists for the GAE modules in their own deployment.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=136863886

javatests/google/registry/server/BUILD

@@ -1,6 +1,6 @@
 package(
     default_testonly = 1,
-    default_visibility = ["//java/google/registry:registry_project"],
+    default_visibility = ["//visibility:public"],
 )
 
 licenses(["notice"])  # Apache 2.0

javatests/google/registry/testing/BUILD

@@ -1,6 +1,6 @@
 package(
     default_testonly = 1,
-    default_visibility = ["//java/google/registry:registry_project"],
+    default_visibility = ["//visibility:public"],
 )
 
 licenses(["notice"])  # Apache 2.0
@@ -20,7 +20,6 @@ java_library(
         "//java/google/registry:env/common/default/WEB-INF/datastore-indexes.xml",
         "//java/google/registry:env/common/default/WEB-INF/queue.xml",
     ] + glob(["*.csv"]),
-    visibility = ["//visibility:public"],
     deps = [
         "//java/com/google/common/annotations",
         "//java/com/google/common/base",

javatests/google/registry/testing/mapreduce/BUILD

@@ -1,6 +1,6 @@
 package(
     default_testonly = 1,
-    default_visibility = ["//java/google/registry:registry_project"],
+    default_visibility = ["//visibility:public"],
 )
 
 licenses(["notice"])  # Apache 2.0
@@ -11,7 +11,6 @@ load("//java/com/google/testing/builddefs:GenTestRules.bzl", "GenTestRules")
 java_library(
     name = "mapreduce",
     srcs = glob(["*.java"]),
-    visibility = ["//visibility:public"],
     deps = [
         "//java/com/google/common/base",
         "//java/com/google/common/collect",