L3 - Default Context:
In order to consolidate event and engine import the existing engine import mediator interface should get extended to reflect the status of the produced importjob per execution. This was succesfully implemented for the current `EventProcessInstanceImportMediator` and simplified test setup to reliably wait for an import cycle to complete. As as consolidation step this aspects needs to be applied to the existing mediator interfaces used in engine context to then completely reuse classes from the engine import in context of the event import as well.
AT:
- the ImportMediator#runImport interface exposes the state of the produced import job using e.g. Futures
- `EngineImportScheduler` & `EventTraceStateProcessingScheduler` offer an interface to run an import cycle and returns a future that completes once all of the mediators of that run completed
- the `SynchronizationElasticsearchImportJob` class used to wait for import cycles to complete is removed, any test logic that waits for imports to complete should use the futures returned from scheduler or mediators