TestApp: Split DataBrokerEngine Interface into multiple Interfaces

[wba2hi]

The DataBrokerEngine grows and grows due to the addition of public methods (e.g. VssSpecs + VssPath + connect), we are already over our allowed limit of 10 methods due to this fact. Therefore we should start splitting the logic inside the DataBrokerEngine into multiple objects.

We should try to share code, where code sharing between Java and Kotlin is possible, however we should not do so for suspend functions as Kotlin Coroutines are not supported out of the box by Java.