Automated istio install

[danisla]

Infrastructure:

• add kustomize to builder image, used to dynamically generate kustomization in k8s_repo step.
• pinned version of terraform-google-vm module.
• migrate clusters to beta clusters module
• enable pod security policy on clusters
• enable workload identity on clusters
• added service account and IAM binding for CNRM system deployment.
• enabled project services to support CNRM, monitoring and cloud tracing APIs used by app.
• improved change detection on terraform null_resource script provisioners.
• terraform fmt all the things.

Ops cloud build:

• install CRDs in separate step using gke-deploy. Prevents race conditions.
• migrate all kubectl apply -f to kustomize kubectl apply -k
• add step to build and apply the multi-cluster service discovery secrets.

K8S Repo:

• migrated cloudbuild step to build_repo.sh
• dynamic build of kustomization for each cluster.
• non-authoritative for the app app-ingress and app-cnrm directories, so they won't be clobbered when the repo is pushed to from outside cloudbuild.

App:

• pod security policies
• workload identities
• migrate manifests to kustomize

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