This only really help with the easiest part of building your inventory
(listing the hosts) as you still need to edit your groups vars and
similar.
The opaqueness of the script does not really help our users to
understand their own inventory.

Furthermore, there is not really a reason that something which is common
to all the Ansible ecosystem should be done in a special way for
Kubespray.

contrib/dind use inventory_builder, which is removed. It overlaps with
the function of kind (Kubernetes in Docker) and has not see change
(apart from linting driven ones) for a long time.

It also does not seem to work (provisioning playbook crash).

There is no need to repeat the full example here, simply state what
variables are.

- The bastion is not needed for a simple example
- All is implicit we can just define our host in groups directly

Our README is currently pretty cluttered:
- Part of the README duplicates docs/getting_started/getting-started.md
-> Remove duplicates and extract useful info into the getting-started.md

- General info on Ansible environment troubleshooting
-> remove most of it as it's not specific to Kubespray, move to
docs/ansible/ansible.md
-> split inventory-related stuff of ansible.md into it's own file. This
should host documentation on how to manages Kubespray inventories in the
future.

ansible.md:
- remove the list of "Unused" variables, as:
  1. It's not accurate
  2. What matters is where users should put their variables