Add a wrapper around monorail.issues.list API

The end-to-end coverage summarizer is intended to display tests which
are unwritten or flaky so that we can measure our percentage of tests
written. (See attached bug.)
In order to do so, we need to query the Monorail API.

This CL adds functions which query the Monorail API, allowing us to
retrieve a list of issues based on some parameters.

The API is called via a service account, which has secret credentials.
The credentials can be found on x20. URL is provided in an error msg.

BUG=b:147815722
TEST=go run fw_e2e_coverage_summarizer.go. Compare results against
Monorail web UI. Try it both with and without credentials file.

Cq-Depend: chromium:2051290
Change-Id: I5a0b21de2f7d34457b60c1ad37bec720fa7a604b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crostestutils/+/2031448
Tested-by: Greg Edelston <gredelston@google.com>
Reviewed-by: Kevin Shelton <kmshelton@chromium.org>
Commit-Queue: Greg Edelston <gredelston@google.com>
2 files changed