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/agent-setup/handlers/main.yml

@@ -0,0 +1,4 @@
+- name: Restart resolved
+  service:
+    name: systemd-resolved
+    state: restarted