Have agent automatically update CRDs in downstream cluster

[dbason]

Currently the downstream clusters require 3 components to be installed: the agent, the client controllers, and the client controller CRDs. In particular the CRDs need to match the version the agent is expecting to install.

The agent plugins are automatically updated, and in the future we will implement updating the agent controllers by updating the agent pod. However this leaves us without a mechanism to update the CRDs.

The crd package in Wrangler may provide a mechanism for doing this. The helm3 controller in k3s currently uses this so we could potentially take inspiration from this:

• https://github.com/k3s-io/helm-controller/blob/master/test/framework/framework.go#L36-L37
• https://github.com/k3s-io/helm-controller/blob/master/test/framework/controller.go#L30

We may need to extend this to add the storage versions and conversion webhooks to the CRDs but can be reviewed as part of an OEP