Replace ReactShallowRenderer with a dependency (#18144)

Closes #17321.

Author: NMinhNguyen

packages/react-test-renderer/package.json

@@ -22,6 +22,7 @@
     "object-assign": "^4.1.1",
     "prop-types": "^15.6.2",
     "react-is": "^16.8.6",
+    "react-shallow-renderer": "^16.12.0",
     "scheduler": "^0.19.0"
   },
   "peerDependencies": {

packages/react-test-renderer/shallow.js

@@ -7,4 +7,4 @@
  * @flow
  */
 
-export {default} from './src/ReactShallowRenderer';
+export {default} from 'react-shallow-renderer';