GitOps example with ArgoCD

[PatrickBladeeman]

This PR adds Argo CD GitOps examples for KubePlus while keeping the runtime sync target lightweight.

The same example content is mirrored in the core kubeplus repo for review and discoverability, and the Argo CD Application manifests point at the lightweight examples repo:

https://github.com/cloud-ark/kubeplus-examples

Changes in this PR:

• Adds examples/multitenancy/application-hosting/hello-world-argocd, matching the corresponding example in cloud-ark/kubeplus-examples.
• Adds examples/multitenancy/application-hosting/wordpress-argocd, matching the corresponding example in cloud-ark/kubeplus-examples.
• Documents where to find the Argo CD GitOps flow from the existing hello-world walkthrough.
• Adds quota fields to the ResourcePolicy Go type so ResourceComposition examples that define quota policy can round-trip cleanly through the KubePlus API.

The key design is that users can read/copy the examples from this repo, but Argo CD should sync from cloud-ark/kubeplus-examples because it is much smaller than the full kubeplus repository.

[devdattakulkarni]

In the commit message add closes with reference to this issue #1437