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.

requirements.yml

@@ -0,0 +1,4 @@
+collections:
+- name: https://github.com/k3s-io/k3s-ansible.git
+  type: git
+  version: 1.0.1