and drive-by simplifications

DATA_DIR is hard-coded in master.cis-yaml
it is not a variable this script has to override

DATA_DIR is a hardcoded variable that should not be modified by the script

the previous format was not well suited to be parsed to a dictionary in python where we were only interested in one key and one value.

the new format directly maps to a dict[str, str] with one call to yaml.safe_load

refactor the file to use clearer function, variable names

extract logic from generate_markdown that is better suited to be in a new function

add a setup_directories function

extract the logic to find the kube bench control files into a function

extract argument parsing to a function

reflect these changes in the jinja template

we support configuring etcd through /etc/default/etcd, therefore
the only configuration relevant to us is through environment variables on the /usr/bin/etcd process.

This commit goes hand in hand with : canonical/kube-bench@a4f580b

see: canonical/kube-bench@0254dd9