Automatic merge from submit-queue (batch tested with PRs 59634, 59821, 57850, 59916, 60032). 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>.
Add cluster-location to GCE instance attributes
**What this PR does / why we need it**:
Exposes cluster location on GCP as instance attribute. In particular, this metadata is useful for exposing metrics to Stackdriver monitoring system and is necessary for some Stackdriver integration components, i.e. Stackdriver Metadata Agent
**Release note**:
```release-note
NONE
```
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