Our GCP storage tests are really flaky right now due to rate limiting.
In theory, this could also impact Terraform users that are
deleting/creating large numbers of Google Cloud Storage buckets at once.
To fix, I'm detecting the specific error code that GCP returns when it's
a rate limit error, and using that with resource.Retry to try the
request again.
This is the first step in removing the config dependency on "project".
This change is backwards-compatible because the value for this new
attribute defaults to the value from the provider.
Paddy