Per #16500 discussion, adds link updates to PR.
Replaces NEP URLs with intersphinx links in these
files:

* doc/HOWTO_RELEASE.rst.txt
* doc/source/dev/howto-docs.rst
* numpy/doc/dispatch.py
* numpy/lib/format.py

and incorporates @rossbar's #16502 change of `config.py`.

Add missing closing brackets, script to generate the list in the PR gh-16051.

It was not clear how to reproduce the slice example with multi dimensional array indexing. I hope the additional example clarifies the equivalence between slice and multi array for new users.

Co-Authored-By: Eric Wieser <wieser.eric@gmail.com>
Co-Authored-By: Anirudh Subramanian <anirudh2290@apache.org>

Cleanup from the dropping of python 2

* PEP 8: "Imports should usually be on separate lines"
* Where modified, sort imported modules alphabetically
* Clean-up unused imports from these expanded lines

Now that 2.7 is gone, there is no need to pop manually from kwarg dictionaries.

Inheriting from object was necessary for Python 2 compatibility to use
new-style classes. In Python 3, this is unnecessary as there are no
old-style classes.

Dropping the object is more idiomatic Python.

As numpy is Python 3 only, these import statements are now unnecessary
and don't alter runtime behavior.