Stable ES features are not always polyfilled when needed

Created by: skoging

Describe the bug

Even with import 'react-app-polyfill/stable', some stable ES features are not polyfilled, such as String#matchAll.

Even importing String#matchAll directly from core-js does not work: import 'core-js/stable/string/match-all'

https://caniuse.com/#feat=mdn-javascript_builtins_string_matchall

Steps to reproduce

(Write your steps here:)

yarn create react-app polyfill-bug
cd polyfill-bug
yarn add react-app-polyfill

// index.js
import 'react-app-polyfill/ie11'
import 'react-app-polyfill/stable'
import 'core-js/stable/string/match-all'

const matches = 'some test string'.matchAll(/s(.)/g);
// IE11 or Safari:
// Error: Object doesn't support property or method 'matchAll'

console.log(Array.from(matches))
// [["te", "e"], ["t ", " "], ["tr", "r"]]

Expected behavior

Polyfill for stable ES features should be part of the bundle when importing react-app-polyfill/stable.

In the case it isn't, explicitly importing the polyfill for the feature should work.