Move the job definitions in-tree, updating them when needed.
This lead to several changes:
- update tox.ini and setup.cfg to align it to the newest standards
(including newer python classifiers);
- no more python 2.x jobs;
- bump hacking requirements to make the pep8 job work with the newest
python releases;
- ignore a few spurious flake8 warnings;
- switch to stestr as test runner;
- update cryptography dependency.
The old barbican simple-crypto job name is still available as an alias
for a while, but it is time to switch away from it, so directly
use the new job.
Depends-On: https://review.opendev.org/771443
Change-Id: Iba7b4106c49e4b492c97097648c7b8f599a2ca4b