pip 6, setuptools 8.3

Merry pipmas!

* Update pip to 6.0.3
* Update setuptools to 8.3 
* Install pip and setuptools from sdist intead of using ensurepip for python3
* Bottle pip and setuptools with python3, pypy, and pypy3 (like python does)
* Add pip tests to python and python3

Closes #35194; fixes #35052, fixes #32254.