upgrade: support the --quiet flag
The command is currently very verbose with a various bit of output being time
sensitive or randomized. The make invocation bulky and hard to match in the
test. We move various message from `ui.write` to `ui.status` in order for the
`--quiet` flag to have effect and helps the situation.
As a side benefit, we can replace the various redirection to > /dev/null with the --quiet flag.
Differential Revision: https://phab.mercurial-scm.org/D8429
#require docutils gettext
$ $TESTDIR/check-gendoc pt_BR
checking for parse errors