Implements WHATWG URL support. Example:
```
var u = new url.URL('http://example.org');
```
Many, many other commits improving the implementation have been squashed
into this backport PR. They are not listed separately here for brevity.
Backport-PR-URL: https://github.com/nodejs/node/pull/17365
PR-URL: https://github.com/nodejs/node/pull/7448
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>
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