The current way to use one of `urllib.request` APIs is like this:
```
import urllib.request
urllib.request.urlretrieve
```

Can we change this to:
```
import urllib
urllib.request.urlretrieve
```
This will require adding 1 line at https://github.com/python/cpython/blob/master/Lib/urllib/__init__.py

This is required because help on `urllib` says that `request` is part of `urllib` suggesting that `urllib.request` should be available if I `import urllib`.
Moreover `import urllib.request` is not at all intuitive.

I can submit a PR if other's think what I'm proposing makes sense.