Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

cluster/gce/list-resources.sh: also list stackdriver logging sinks

**What this PR does / why we need it**: we seem to be logging stackdriver logging sinks on GCE, likely because we're not keeping track of them. (ref https://github.com/kubernetes/test-infra/issues/7295)

This doesn't fix the leaks, but it'll hopefully help us detect when that happens.

**Release note**:

```release-note
NONE
```

cc @krzyzacy @crassirostris @summit