Remove lodash from core (#2827)

* Remove `lodash-es` dependency

* Replace `escapeRegExp` with home-made util

* Replace `throttle` with `throttle-debounce` library

* Use native browser methods for `deepFlatten`

We need a polyfill for iOS 11 and below. I think using a native method with this polyfill is better than having our own function instead, even if the bundle size is ~150B more.

* Save a few bytes in `escapeRegExp`

* Fix typo in comment

* Undo import re-organisation

* Use spread instead of slice

* Use smaller Array.flat polyfill from MDN

* Export new utils in `compat.js`

js/src/common/index.js

@@ -23,3 +23,5 @@ patchMithril(window);
 import * as Extend from './extend/index';
 
 export { Extend };
+
+import './utils/arrayFlatPolyfill';