TypeMissingException for very old TaskActivity, even for which orchestration have finished long back.

Problem statement:
- We are observing quite some task-activities that are failing with TypeMissing exception.
- This results in backoff and reduces the performance significantly.
- This becomes interesting, especially when the type (TaskActivity/TaskOrchestration) is intentionally removed assuming old ones would die eventually. (Especially for the case of testing).
- We can't delete them manually, as message is read by taskhubworker and is hidden.
- There are cases where orchestrator is already completed, while task-activity is still trying to run.

Ask:
- Can there be a way, where one can provide the ETA for type, implies, when it is picked up for processing, if the time it queued was older than a threshold interval, just mark it finished.
- For task-activities for which orchestration is already completed, can those just be removed without processing?
- A way to kill one type of type (say orchestration of type A, just remove all those entries from the queue, similarly for task-activity and other work-items). Like some API etc. E.g., AddNoOpTaskOrchestration, AddNoOpTaskActivity.