[WIP]add snapshotter

[mowangdk]

Add snapshotter to aio poc

• Require modification to external-snapshotter

[mowangdk]

relies: kubernetes-csi/external-snapshotter#1336

[mauriciopoppe]

Having a POC would be good but I think we should write details about how is it that we're planning on integrating the multiple artifacts from external-snapshotter.

• 1 unified sidecar (all the sidecar repos), 1 control plane controller, 1 webhook
• 1 single artifact that can work in all the modes above
• What about the snapshotter client? Do we have other sidecars with clients? If we need to make a bug fix in one client we'd need to create a new release of the monorepo even if other clients are good.

[mowangdk]

Having a POC would be good but I think we should write details about how is it that we're planning on integrating the multiple artifacts from external-snapshotter.

• 1 unified sidecar (all the sidecar repos), 1 control plane controller, 1 webhook
• 1 single artifact that can work in all the modes above
• What about the snapshotter client? Do we have other sidecars with clients? If we need to make a bug fix in one client we'd need to create a new release of the monorepo even if other clients are good.

Based on our KEP, I believe1 unified sidecar (all the sidecar repos), 1 control plane controller, 1 webhook with the original design intentions.

I'd researched that VolumeAttributesClass is a built-in resource, while VolumePopulator is a vendor-defined CRD, hence they don't share a similar scenario.

And integrating the VolumeSnapshot-related client into the AIO project should be fine if it's the only client we have. what do you guys think? @ConnorJC3 @iltyty

[mowangdk]

https://github.com/kubernetes-csi/external-snapshotter/pull/1355/changes