move roles, files and templates dirs out of playbook dir into root dir

Because of how Ansible local relative search paths work, the global
"files" and "templates" directories need to be next to the playbooks.
However its not intuitive to look into the "playbooks" directory to find
the files and templates for a host.
Therefore move them out of the "playbooks" directory into the root
directory and add symlinks so everything still works.

Similarly for local roles, they also need to be next to the playbooks.
So for a nicer structure, move the "roles" directory out into the root
directory as well and add a symlink so everything still works.

Also see:
https://docs.ansible.com/ansible/latest/playbook_guide/playbook_pathing.html#resolving-local-relative-paths
https://docs.ansible.com/ansible/latest/playbook_guide/playbooks_reuse_roles.html#storing-and-finding-roles

roles/apt_update_and_upgrade/README.md

@@ -0,0 +1,11 @@
+# Role `apt_update_and_upgrade`
+
+This role does an `apt-get update`, `apt-get dist-upgrade` and a potential reboot (if packages got upgraded) on the specified hosts.
+
+## `hosts`
+
+The `hosts` for this role need to be the VMs, which should be updated and upgraded.
+
+## Required Variables
+
+This role doesn't have any required variables.

roles/apt_update_and_upgrade/handlers/main.yaml

@@ -0,0 +1,3 @@
+- name: reboot the system
+  become: true
+  ansible.builtin.reboot:

roles/apt_update_and_upgrade/tasks/main.yaml

@@ -0,0 +1,13 @@
+- name: update, upgrade and potentially reboot
+  become: true
+  block:
+    - name: apt-get update
+      ansible.builtin.apt:
+        update-cache: true
+
+    - name: apt-get dist-upgrade
+      ansible.builtin.apt:
+        upgrade: dist
+      register: apt_update_and_upgrade__upgrade_result
+      notify:
+        - reboot the system