Create a scenario that integrates a Witness node

[glovecchi0]

Simulate and document a scenario that includes 1 Witness node in a 2-node Harvester cluster.

[glovecchi0]

Feature flag.
If the witness variable is true, then create two nodes with the default role and one with the witness role.

Modify the join_cloud_config_yaml.tpl file by adding the variable install.role = ${role} and manage it in the main project.
If witness is true, then it becomes witness; otherwise, it becomes default.

It would be ideal to force the deployment of 2 default nodes and 1 witness, ignoring the default value of the harvester_node_count variable.