Add gp3 storageclass

We add this unconditionally to all clusters for simplification,
so we can set storageClass: gp3 for new clusters that come up on
AWS without issue. This doesn't change the default, and does not
change the storageclass in existing clusters. In addition to using
gp3, it also sets reclaimPolicy to Retain, so if the PVC is deleted,
it does not delete the PV or the underlying EBS volume.

Ref 2i2c-org#2906
Ref 2i2c-org#2717

helm-charts/support/templates/storageclass/gp3.yaml

@@ -0,0 +1,18 @@
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: gp3
+# Use the AWS EBS CSI provisioner
+provisioner: ebs.csi.aws.com
+parameters:
+  # gp3 is cheaper than gp2
+  type: gp3
+  fsType: ext4
+# Do not delete the underlying EBS volume whenever this PV & PVC
+# are deleted! This allows us recovery in case of accidental deletion
+reclaimPolicy: Retain
+# Create the EBS volume only when the pod consuming it tries to use it.
+# This ensures the EBS volume is created in the correct *zone*, so we
+# don't end up with issues where the volume is in a different zone (but
+# same region) as our pods.
+volumeBindingMode: WaitForFirstConsumer