[autotest]: Refactor bug filing.

This creates a new Bug class that TestFailure now derives from. This allows us
to file bugs for issues that are not test failures.

BUG=chromium:254256
TEST=Unit tests and ran the dummy suite and saw that the tests were deduped.

Change-Id: I104489e9627a64506fc9c206392f1297fa538c44
Reviewed-on: https://gerrit.chromium.org/gerrit/65898
Reviewed-by: Prashanth Balasubramanian <beeps@chromium.org>
Reviewed-by: Keyar Hood <keyar@chromium.org>
Tested-by: Keyar Hood <keyar@chromium.org>
Commit-Queue: Keyar Hood <keyar@chromium.org>
5 files changed