Add CSI snapshot CRDs/controller/webhook

[brandond]

Proposed Changes

Add a bundled HelmChart for the CSI snapshot CRDs, controller, and validation webhook. Ref: https://kubernetes.io/docs/concepts/storage/volume-snapshots/

The CRDs and snapshot controller installations are the responsibility of the Kubernetes distribution.

Uses the charts from piraeusdatastore because upstream does not want to maintain their own charts, as per kubernetes-csi/external-snapshotter#622 (comment)

• DECISION POINT: Do we want to enable this by default? If not, what is our model for shipping disabled-by-default components?
• builds on Stage the Traefik charts through k3s-charts #6519

Types of Changes

new feature

Verification

Start k3s without --disable=snapshot-controller; note deployment of two new pods.

Testing

• tbd

Linked Issues

• Consider including the snapshot controller + related resources as part of k3s #2865

User-Facing Change

K3s now bundles the Kubernetes SIG-Storage CSI Snapshot Controller and Validating Webhook, as a HelmChart. This may be disabled by starting k3s with `--disable=snapshot-controller`.

Further Comments

[brandond]

We've decided not to do this, in favor of covering use of the piraeusdatastore chart in the docs. I'll open a new ADR to cover this decision.

[omidraha]

I reached this issue through longhorn/longhorn#2551 (comment)