Allow to define default launch arguments

[retyui]

I face with annoying thing that I have to define arguments in each test flow (contestant values, won't be changed)

- launchApp:
    appId: "com.example.app"
    arguments: 
       isMaestro: true
       turnOffAnalytics: true

Will be great to have ability to define a default launch arguments in config.yaml that will be used all the time by launchApp command