tests: change the fixer commands to use the buffer attribute on stdio objects Otherwise `\r` was getting injected into the fixed lines and throwing off the commit hashes on Windows when the fixer is invoked with py3. Differential Revision: https://phab.mercurial-scm.org/D10637

tests: stabilize test-persistent-nodemap.t on Windows Several issues here: - Hooks can't invoke shell scripts on Windows, so use `sh` to launch - `dd` in MSYS only recognizes `status=noxfer` - The `PATH` updating triggered a massive slowdown, but is no longer needed I have no idea why, but removing the `PATH` update substantially increased the speed of the test. It was running finishing at ~4:30 with `--debug` and ~14:50 without it, but now completes in ~2:20 on my Windows laptop. Differential Revision: https://phab.mercurial-scm.org/D10636