Support custom argo overrides on spokes

[mbaldessari]

If you set the following you can customize the "main" ArgoCD instance we
create on spokes:

acm:
  customArgoYaml:
    controller:
      resources:
        limits:
          cpu: "4"
          memory: 17Gi

This gets deepmerged with the default yaml we normally inject.

Tested with empty customArgoYaml and with the snippet above which got me (sno2 was the spoke):

$ export KUBECONFIG=~/sno2-kubeconfig
$ oc get -n vp-gitops argocd vp-gitops -o jsonpath='{.spec.controller.resources.limits}' | jq .
{
  "cpu": "4",
  "memory": "17Gi"
}