This fixes `test_deadlock_resubmit_queued_tasks_fast`. The problem:
- an "old" TaskState `f-0` is forgotten and removed from `queued` HeapSet. Internally, this removes it from a set, but a weakref is still on the heap
- a new TaskState `f-0` is added to the HeapSet. It's pushed onto the heap, but since its priority is higher (newer generation), it comes after the old `f-0` object that's still on the front of the heap
- `pop` pops old `f-0` off the heap. The weakref is still alive (for whatever reason). `value in self._data` (the set) is True, because the _hash_ of old `f-0` and new `f-0` are the same (same key). So we return the stale, old TaskState object.

Much like `WorkerState`s, there should be exactly 1 `TaskState` instance per task. If there are multiple instances with the same key, they are different tasks, and have different state. xref dask#7372, dask#7356.