fix(ci): retry transient DNS failures on remote downloads and cilium install (#690)

- Add shared download_retries/download_delay defaults in k3s_server and k3s_server_post roles
- Retry calico CRD and Tigera operator manifest downloads
- Retry Cilium CLI download and cilium install/upgrade command
- Retry kube-vip cloud provider and MetalLB manifest downloads
- The CI runner's resolver intermittently times out on GitHub-hosted domains

roles/k3s_server/tasks/metallb.yml

@@ -15,6 +15,10 @@
     owner: root
     group: root
     mode: "0644"
+  register: metallb_manifest_download
+  retries: "{{ download_retries }}"
+  delay: "{{ download_delay }}"
+  until: metallb_manifest_download is succeeded
   when: ansible_hostname == hostvars[groups[group_name_master | default('master')][0]]['ansible_hostname']
 
 - name: Set image versions in manifest for metallb-{{ metal_lb_type }}