fix(metallb): deploy MetalLB with a non-BGP Cilium CNI (#692)

- Correct the Deploy metallb manifest/pool when condition so MetalLB is
  installed whenever kube-vip does not own the VIP range and Cilium BGP
  is disabled
- The previous guard (cilium_bgp is not defined or cilium_iface is not
  defined) skipped MetalLB whenever cilium_iface was set, breaking the
  cilium + MetalLB scenario
- Use cilium_bgp | default(false) | bool to stay safe when Cilium vars are
  not in scope (#644) while still deploying MetalLB for non-BGP Cilium
- Retry the converge-side MetalLB resource wait so a transient kube API
  ServiceUnavailable does not abort the converge play
- Add a regression test that evaluates both when conditions across flannel,
  calico, non-BGP cilium, BGP cilium, and kube-vip scenarios

ci: skip CI for Dependabot pull requests

- Add an actor guard to the CI workflow jobs so automatic Dependabot PRs
  do not consume the shared self-hosted runner
- Dependabot CI runs need maintainer approval instead of auto-running

roles/k3s_server_post/defaults/main.yml

@@ -23,6 +23,13 @@ cilium_mode: native
 cilium_tag: v1.20.0
 cilium_cli_tag: v0.19.7
 
+# Shared retry/delay for remote manifest, asset downloads, and waiting on
+# Kubernetes resources. The CI runner's resolver intermittently times out on
+# GitHub-hosted domains and the kube API can transiently return
+# ServiceUnavailable, so retry transient DNS/network/API failures.
+download_retries: 5
+download_delay: 10
+
 cluster_cidr: 10.52.0.0/16
 enable_bpf_masquerade: true
 kube_proxy_replacement: true