Merge infra and k3 into one directory again

Since I don't have multiple terraform steps anymore it simply doesn't
make sense to me anymore to split all tasks into separate folders.
Instead I try to be as clear as possible in the README to make it easy
to follow the structure in the future without too much headache.

roles/k8s-setup/defaults/main.yml

@@ -0,0 +1,3 @@
+cert_manager_state: present
+cert_manager_version: v1.18.2
+letsencrypt_clusterissuers: {}