[add_cloud_metadata][GCP] Add instance.name

[kimxogus]

Describe the enhancement:
Add .cloud.instance.name to add_cloud_metadata processor in Google Cloud Platform

Describe a specific use case for the enhancement or feature:

In gke console, instance.id is not used, so it's hard to identity gke node using instance.id. It would be much more useful having instance.name

[botelastic]

This issue doesn't have a Team:<team> label.