logilab-common #204933 configuration: Have a method that produce an easy to use representatin of the current configuration [in-progress]

This should be done mostly by extracting the method from the "generate_config" method.

prioritynormal
typeenhancement
done in<not specified>
load0.500
load left0.500
closed by<not specified>
patch[configuration] extract a YAML-friendly build_config_struct function from generate_config (closes #204933) [in-progress]