downloads: split file and containers (#13581)

Splits the definitions into two dicts, while joining then for now to
preserve the downloads dict.

Update all consumers of the variables, which are roughly:
- manual includes of the download role (which will be removed in the
  short future)
- install tasks using the resolved 'dest' to find the artefacts

This will make further division of the downloads role easier.

roles/kubernetes-apps/argocd/tasks/main.yml

@@ -12,7 +12,7 @@
     cmd: >
       {{ kubectl }} apply -n {{ argocd_namespace }}
       --server-side=true --force-conflicts --field-manager=kubespray
-      -f - -f {{ downloads.argocd_install.dest }}
+      -f - -f {{ downloads_file.argocd_install.dest }}
     stdin: "{{ ns_object | to_json }}"
 
 # https://github.com/argoproj/argo-cd/blob/master/docs/faq.md#i-forgot-the-admin-password-how-do-i-reset-it