Make auth be able to generate id_token. Some services on Cloud Run will
need it (e.g. luci-config v2).
Bug: 1487020
Change-Id: Icfe95002f93ee552b99ab2694c7b777e2322484b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4899437
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Commit-Queue: Yuanjun Huang <yuanjunh@google.com>