[Cluster] Add Manual Cluster

[AntyaDev]

• AgentsCount - should be mandatory
• Agent should stop after the session (by default)

{
    "TestSuite": "my test suite",
    "TestName": "my test",

    "ClusterSettings": {

        "ManualCluster": {
            "ClusterId": "test_cluster",
            "NATSServerURL": "nats://localhost",

            "Coordinator": {
                "TargetScenarios": ["test_scenario"]
            },

            "Agent": {
                "AgentGroups": [
                    { "Group": "1", "TargetScenarios": ["test_scenario_1"] },
                    { "Group": "2", "TargetScenarios": ["test_scenario_2"] }
                ],
                
                "AgentsCount": 1
            }
        }

    }    
}