Modify the exploration backend to support multi-rate schedules
While the Z3-backend does not support multi-rate schedules as of now
Hence, any restrictions limiting the calculation of multi-rate schedules shall be moved from backend-agnostic parts of the exploration backends to the respective backends.
ExplorationTimingConstraintUtils, for instance, overwrites the
periods of all tasks to equal. This shall be done in the Z3-backend
(with an appropriate notification for the user), while leaving the
periods unchanged for other backends.
(from redmine: issue id 4085, created on 2020-11-19)
- relates #4088