unionrepo: fix `revdiff` implementation to use `rawdata` The parent code is using rawdata so we should use it here. Before this change, union repo was probably broken with some flag processors.

unionrepo: get rid of `baserevision` The method is not called anywhere anymore, so we can safely drop it. Some of the comment get moved to `baserevdiff` because we did not got rid of it (yet).

unionrepo: use a lower level overide in unionrepo too The unionrepo class also have a strange `baserevision` hack, let's try to get ride of it too.

bundlerepo: drop the custom `rawdata` implementation We can rely on the main one now.

bundlerepo: drop the `baserevision` hack It is not used anywhere anymore, so we can safely drop it.

bundlerepo: simplify code to take advantage of `_rawtext` In the revlog code, the code getting the raw text is now isolated. We take advantage of this to simplify the bundlerepo code.

merge with stable

rust: run cargo fmt

py3: use pycompat.maplist() in chgserver test-chg.t almost passes on py3 after this patch. Differential Revision: https://phab.mercurial-scm.org/D6771

run-tests: handle --local before --with-hg We no longer support them both together, so this is now safe to do. By checking --local first, we avoid error out about an invalid --with-hg script if --local was also given (we instead tell the user that the options are mutually exclusive). I also had to wrap the 'binpath' we pass to setattr() in _strpath() to keep `python3 run-tests.py -l` working. That change also made `python3 run-tests.py -l --chg` work, which was the reason for this series. Differential Revision: https://phab.mercurial-scm.org/D6760