progress: check what type of progress bar to use only once per topic
This seems to have sped up `hg perfprogress` from 1.78 s to 1.41 s.
Differential Revision: https://phab.mercurial-scm.org/D5530
from __future__ import absolute_importimport pkgutil__path__ = pkgutil.extend_path(__path__, __name__)