Move worker protocol and babelRegisterOnly into their own packages

Summary: Moves the implementation of Buck’s worker protocol into its own package and babelRegisterOnly for better reusability.

Reviewed By: rafeca

Differential Revision: D7666896

fbshipit-source-id: ae297494ced3b8dd1f9d90983a640643d6ce7896

jest/preprocessor.js

@@ -15,7 +15,7 @@ const {transformSync: babelTransformSync} = require('@babel/core');
 /* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
  * found when Flow v0.54 was deployed. To see the error delete this comment and
  * run Flow. */
-const babelRegisterOnly = require('metro/src/babelRegisterOnly');
+const babelRegisterOnly = require('metro-babel-register');
 /* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
  * found when Flow v0.54 was deployed. To see the error delete this comment and
  * run Flow. */

package.json

@@ -167,6 +167,7 @@
     "inquirer": "^3.0.6",
     "lodash": "^4.17.5",
     "metro": "^0.34.0",
+    "metro-babel-register": "^0.34.1",
     "metro-core": "^0.34.0",
     "mime": "^1.3.4",
     "minimist": "^1.2.0",

setupBabel.js

@@ -7,7 +7,7 @@
 
 'use strict';
 
-const babelRegisterOnly = require('metro/src/babelRegisterOnly');
+const babelRegisterOnly = require('metro-babel-register');
 const escapeRegExp = require('lodash/escapeRegExp');
 const path = require('path');