mgr/ansible: Add/remove hosts

mgr/ansible: Add/remove hosts

- Implementation of operations add/rm hosts
- Improvement of error management in Ansible Runner Service Client

- Addressed @sebastian-philipp suggestions and findings
- Remove the <role> parameter of hosts operations.
Now all the hosts are placed by default in a specific Ansible Inventory group called <orchestrator>.
Discussion on-going about to keep Host management API endpoint or not.
If hosts management is removed, further modifications will be needed to:
- Keep updated the <host inventory> in the orchestrator
- Manage hosts groups when operations are executed
- Adapted new commands (host add/rm) to use to the new <orchestrator_cli> syntax

- Improved error management
- Added return information to Add/remove host methods docstring

- Removed redundant exceptions following @sebastian-philipp suggestion

- Removed duplicated code
- Removed extra space

- Fixed unit tests
- Improved error management in launch playbook

- removed unused param in docstring (orchestrator.py)

Signed-off-by: Juan Miguel Olmo Martínez <jolmomar@redhat.com>