Expose base endpoint on ArgoCD ApplicationSet Controller for GKE Ingress

[patrickblackjr]

GKE Ingress requires a GET request to return 200 OK before it will route any traffic. The ArgoCD ApplicationSet Controller should have an endpoint that returns this so it can be easily exposed via an ingress.

Per the Webhook Configurations documentation, this webhook needs to be exposed via a separate ingress to allow for the Git Generator or the Pull Request Generator.

Would the project be open to a PR adding this functionality? It could be perhaps be optionally enabled via a configuration item if there were any security concerns and some users didn't prefer to use it.

[patrickblackjr]

#19559 opened as a proposal.