[autotest] Create generic bug filer function.

This makes it easier to file simple generic bugs. The user doesn't need to
create the Bug, create the Reporter and then call report().

BUG=None
TEST=Unittests. Manual test for passing_experimental.py.

Change-Id: I6d27cfa6a72b8dd4d22d8301b1c3105b90363a5a
Reviewed-on: https://chromium-review.googlesource.com/67009
Reviewed-by: Prashanth Balasubramanian <beeps@chromium.org>
Tested-by: Keyar Hood <keyar@chromium.org>
Commit-Queue: Prashanth Balasubramanian <beeps@chromium.org>
6 files changed