Add a new prod region

1. Provision a Seed GKE cluster with Pulumi in https://github.com/tidbcloud/infra/tree/prod/deploy/gke

2. Configure the new region gke cluster to ArgoCD following instructions in [GKE Cluster](../argocd/README.md)

3. Deploy [external-secrets-operator](../app-registry/external-secrets-operator.yaml) and a default [cluster secretstore](../secretstore/envs) in the GKE cluster

4. Deploy the gke-provider to new region

``` shell
region=xxxx
cp -r gke-provider/envs/prod-us-central1 gke-provider/envs/prod-${region}
# Change config.yaml in new region `gke-provider/envs/prod-${region}/config.yaml`
# Register the gke-provider in new region `app-registry/gke-provider.yaml`
```

Currently the region and whitelist IP needs to be changed accordingly. For whitelist IPs, we just need to update the seed NAT IP. The seed NAT IPs can be retrieved by `gcloud compute addresses list --project dbaas-prod| grep nat | grep seed`