Babel 7 (#23966)

* use .babelrc.js, compile bundled/non-bundled with loose mode

* add back helper, exclude typeof transform

.babelrc.js

@@ -0,0 +1,16 @@
+module.exports = {
+  presets: [
+    [
+      'env',
+      {
+        loose: true,
+        modules: false,
+        exclude: ['transform-es2015-typeof-symbol']
+      }
+    ]
+  ],
+  plugins: [
+    process.env.ROLLUP && 'external-helpers',
+    process.env.PLUGINS && 'transform-es2015-modules-strip',
+  ].filter(Boolean)
+};