roachtest: improve handling of cluster creation errors from cloud provider

[renatolabs]

We have been seeing a number of cluster creation errors every night on roachtest nightly runs. Part of this has to do with GCP not having enough resources on us-east1-b, where we create VMs by default [1]. These errors typically look like:

The zone 'projects/cockroach-ephemeral/zones/us-east1-b' does not have enough
  resources available to fulfill the request.  '(resource type:compute)'.

Recent example: #108629 (comment).

The error message includes a computer-readable payload that indicates other AZs where there are resources available for the request that failed; that information should be in errorInfo.metadatas.zonesAvailable:

- errorInfo:
    domain: compute.googleapis.com
    metadatas:
      attachment: local-ssd:16
      vmType: n2-highcpu-96
      zone: us-east1-b
      zonesAvailable: us-east1-c,us-east1-d
    reason: resource_availability

(extracted from the error message linked above).

Roachtest could be smarter about its cluster creation retry mechanism and take this information into account.

It also wouldn't hurt to rotate the default AZ (i.e., use us-east1-{b,c,d}), or even use us-central as well.

[1]

cockroach/pkg/roachprod/vm/gce/gcloud.go

Line 969 in bab4335

zones = []string{defaultZones[0]}

Jira issue: CRDB-33544

[blathers-crl]

cc @cockroachdb/test-eng