[autotest] Report how many times an autofiled bug has been seen.

In the run_suite output, the text for any link to a bug will include
an estimate of the number of times the bug has been reported, or
describe it as new if this is the first occurrence.

BUG=chromium:265464
TEST=unit tests and run_suite with the dummy suite in a local instance

Change-Id: I13a57a2a548adb4b5eff52fc1b438ec8e5b552b7
Reviewed-on: https://chromium-review.googlesource.com/66846
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Prashanth Balasubramanian <beeps@chromium.org>
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
7 files changed