Add argocd-apps as a subchart to argocd

As of version 5.0.0 of ArgoCD (1.46.1 BB) the server.additionalApplications and server.additionalProjects configs have been moved outside of the main ArgoCD chart. This MR will bring the new chart in as a sub-chart so that the configuration can continue to be managed without any additional configuration to BB.

The subchart is a copy of argocd-apps with no changes.

More details can be found here: big-bang/bigbang#1436 (closed)