fix(engine): add suspension state to mysql tables

contributes to CAM-447
test(engine): test optimistic locking for execution suspension

- ensures that the execution revision is updated in case of a
cascading process definition suspension such that concurrent
modifications fail with an optimistic locking exception

contributes to CAM-447
fix(engine): simplify update suspension state statements

- fixes issues on postgres with table aliases for execution and task

contributes to CAM-447