Move generic configuration values generation from stage_0 to init_instance and default values

[aurelienmaury]

When applying the stage_0 role, we generate a bunch of variables in the local instance directory as output.

When an operator wants to supply its own infrastructure, a lot of these variables could help him to accelerate its comprehension and adaptation to its technical case.

Sort out in :

• <project root>/roles/stage_0/templates/mono/out.stage0.hashistack.yml.j2
• <project root>/roles/stage_0/templates/multi/out.stage0.hashistack.yml.j2
• <project root>/roles/stage_0/templates/multi/out.stage0.hashistack_sre.yml.j2

what needs to:

• be set as default values in corresponding roles
• be moved to the templating done by playbooks/00_init_instance.yml
• remain in place and be documented