crash: Remove glib from crash_reporter

As part of the minimization effort, refactor crash_reporter code to
not depend directly on glib.

BUG=brillo:87, brillo:88, chromium:435314
TEST=`FEATURES=test emerge-panther libchromeos debugd crash-reporter`
TEST=Enabled crash reports; Browsed to chrome://crash; crash files \
     generated; `FORCE_OFFICIAL=1 SECONDS_SEND_SPREAD=1 crash_sender` \
     /var/log/messages shows crash id, report shows all expected files
TEST=`cbuildbot --remote -p chromiumos/platform2 amd64-generic-full`
CQ-DEPEND=I00331e0bf29195b41cd84d4495ab47738a5a41de
CQ-DEPEND=I9df752d8995773adb56fab34dd97626f3ddf1765

Change-Id: I48b366198a7f89ca55259603cf8470e4d59321bf
Reviewed-on: https://chromium-review.googlesource.com/246441


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