agent: provide conformance test workloads to validate node setup

We should define a set of test workloads for validating the node setup. We can run them as part of the cluster validation. We can include:

- GPU devices validation
- node-to-node connectivity
- outbound connectivity

Start by locating the cluster validation entry point and the node setup logic. Define workloads covering GPU device validation, node-to-node connectivity, and outbound connectivity, then integrate them into cluster validation. Done means all three checks run as part of validation and report whether the node setup is conformant.

Written by the indexing model from the issue text.