tests: make log style a little easier to read in test-copytrace-heuristics.t
Revision numbers are much shorter and easier to read (especially
compared to the full nodeids that were used here), so I switched to
that. That's also what almost all the commands used (e.g. `hg rebase
-s . -d 1`). I updated the two instances that used nodeids. I also
made some other little cleanups to the log templates.
Differential Revision: https://phab.mercurial-scm.org/D6279