inject instance of ErrorReport::Reporter into IncomingMessageProcessor

fixes CNVS-12150

QA Test Plan:
- regression test incoming mail (check error reports)

Change-Id: Ib25cf1ad78cb76db3da5d97cf6e33740e50d472d
Reviewed-on: https://gerrit.instructure.com/32679
Reviewed-by: Braden Anderson <banderson@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Joel Hough <joel@instructure.com>