buildbot, deps: remove; python -> python2

[classabbyamp]

! This should not be merged until the necessary infra changes happen !

Removes buildbot and all python2 dependencies in the dependency tree that became unused as a result.

as buildbot is the last remaining blocker of the python 2 removal project, it is also removed here

[classabbyamp]

I've moved the following packages:

python -> python2
python-devel -> python2-devel
python-tkinter -> python2-tkinter
python-pip -> python2-pip
python-setuptools -> python2-setuptools

python and python-devel became a metapackage with a warning about impending migration to python 3; python-pip, python-setuptools, and python-tkinter became transitional packages.

I put your name on python2-pip and python2-setuptools.