Install openbao-plugin-secrets-rancher on vault nodes

Lays down the rancher secrets-engine plugin binary in the OpenBao plugin
directory (/opt/openbao-plugins/vault-plugin-secrets-rancher) so terraform-vault
can register and mount it. Package comes from the rpm-internal repo.

- Add openbao-plugin-secrets-rancher to profiles::packages::include on the vault
  storage role.

hieradata/roles/infra/storage/vault.yaml

@@ -30,3 +30,4 @@ profiles::packages::include:
   openbao-plugins: {}
   openbao-plugin-secrets-litellm: {}
   openbao-plugin-secrets-gpg: {}
+  openbao-plugin-secrets-rancher: {}