Add Scenario Weight to introduce dynamic workload distribution

[AntyaDev]

Reference: #662
Documentation link

Scenario.Create("")
        .WithLoadSimulations()
        .WithWeight(3)

or via JSON config

{
    "GlobalSettings": {
        "ScenariosSettings": [
          {
                "ScenarioName": "test_youtube",
                "Weight": 10
          }
        ]
    }
}