terraform: setup experimental nodepool with ephemeral local ssd for k8s-infra-prow-build

[spiffxp]

Related:

• Part of: Migrate k8s-infra-prow-build to a nodepool with more IOPS #1187

Add terraform to provision a new nodepool with ephemeral storage backed by local SSDs, ref:

• https://cloud.google.com/kubernetes-engine/docs/how-to/persistent-volumes/local-ssd
• https://registry.terraform.io/providers/hashicorp/google/latest/docs/resources/container_cluster#ephemeral_storage_config

Taint the nodepool such that only jobs that tolerate ephemeral-ssd-experiment=true will schedule to the new nodepool

Use this to experiment with some canary jobs to see if everything behaves as expected

[k8s-ci-robot]

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[dims]

/lgtm