crash: Convert list_proxies to chromeos-dbus-bindings generator

Switch list_proxies to using chromeos-dbus-bindings generator
in order to remove the glib dependency.

BUG=brillo:89
TEST=`FEATURES=test emerge-panther crash-reporter`
TEST=manually tested `list_proxies --quiet      \
       https://clieents2.google.com/cr/report`

Change-Id: Ic52277b2e14514376f4d55e627e1651d9ef566c5
Reviewed-on: https://chromium-review.googlesource.com/248781


Reviewed-by: Dan Erat <derat@chromium.org>
Trybot-Ready: Dan Erat <derat@chromium.org>
Commit-Queue: Steve Fung <stevefung@chromium.org>
Tested-by: Steve Fung <stevefung@chromium.org>