Add distributor queue and function

[mcopik]

The implementation does not include the new type of queue and function.

• [x] Change writer implementation to push to the new queue.
• [x] Allocate queues.
• [x] Implement function.
• [ ] Parallelize across regions.
• [x] Invoke watchers.
• [ ] Sort requests from writers.
• [ ] Load/store state of the function in the storage.
• [ ] Formalize fault tolerance.