Packer bootstrap tweaks

Much speed by using our Geo mirror + maximum freshness by not hard coding the bootstrap version anymore + extreme future-proofness by creating the temporary server with Ubuntu 22.04. ️

packer/archlinux.json

@@ -10,7 +10,7 @@
             "custom_image": "archlinux"
         },
         "token": "{{ user `hetzner_cloud_api_key` }}",
-        "image": "ubuntu-20.04",
+        "image": "ubuntu-22.04",
         "server_type": "cx11",
         "ssh_username": "root",
         "location": "fsn1",