test: formalize exposure of internal bindings

moves exposed internalBindings to a single location with short
guidelines on how to expose them and a warning for users should they
come across it

lib/internal/test/binding.js

@@ -0,0 +1,13 @@
+'use strict';
+
+process.emitWarning(
+  'These APIs are exposed only for testing and are not ' +
+  'tracked by any versioning system or deprecation process.',
+  'internal/test/binding');
+
+// These exports should be scoped as specifically as possible
+// to avoid exposing APIs because even with that warning and
+// this file being internal people will still try to abuse it.
+module.exports = {
+  ModuleWrap: internalBinding('module_wrap').ModuleWrap,
+};

node.gyp

@@ -107,7 +107,6 @@
       'lib/internal/loader/DefaultResolve.js',
       'lib/internal/loader/ModuleJob.js',
       'lib/internal/loader/ModuleMap.js',
-      'lib/internal/loader/ModuleWrap.js',
       'lib/internal/loader/Translators.js',
       'lib/internal/safe_globals.js',
       'lib/internal/net.js',
@@ -125,6 +124,7 @@
       'lib/internal/repl.js',
       'lib/internal/repl/await.js',
       'lib/internal/socket_list.js',
+      'lib/internal/test/binding.js',
       'lib/internal/test/unicode.js',
       'lib/internal/timers.js',
       'lib/internal/tls.js',

test/parallel/test-internal-module-wrap.js

@@ -6,7 +6,7 @@ const common = require('../common');
 common.crashOnUnhandledRejection();
 const assert = require('assert');
 
-const ModuleWrap = require('internal/loader/ModuleWrap');
+const { ModuleWrap } = require('internal/test/binding');
 const { getPromiseDetails, isPromise } = process.binding('util');
 const setTimeoutAsync = require('util').promisify(setTimeout);