Support "agent-tls-mode" in agentmanagement

[manno]

This will be on the cluster resource, agents need to redeploy when changing it.

Needs support in Rancher's fleetchart controller, too.

We will have to adapt https://github.com/rancher/rancher/blob/release/v2.9/pkg/controllers/dashboard/fleetcharts/controller.go#L36-L42 to watch the new setting and reinstall fleet. That would change the config and we can use the AgentConfigChange field on the cluster to update the downstream agents. Same as APIServer URL/CA changes.