DM: verbose and quiet logging

DM: verbose and quiet logging

If you pass no flags, output is pretty much unchanged from today: calls to
info() go to the console, calls to vlog() are ignored.

If you pass --verbose and -w dir, all calls to info(), vlog() and all of stderr
are redirected to dir/verbose.log.  info() calls also go to the console,
unless you pass --quiet, in which case nothing goes to the console at all.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1771143002

Review URL: https://codereview.chromium.org/1771143002