Move bisect-perf-regression.py into auto_bisect directory.
The purpose of this is to continue gathering all the related code together, and to make it easier to run pylint/tests for the main module which still contains most of the code.
After doing this, pylint and the tests caught a couple of things -- one unused variable name, and after the script changed directory, some of the paths had to be modified as well.
BUG=
Review URL: https://codereview.chromium.org/
564663002
Cr-Commit-Position: refs/heads/master@{#296847}