Negative occupancy causes state machine corruption

For some reason, `WorkerState.network_occ` can drop below zero and cause the state machine to corrupt.

Reproducer:

```python
import coiled
import dask
import dask.array as da
cluster = coiled.Cluster(
n_workers=10,
worker_vm_types=["m6i.large"],
worker_disk_size=128
)
client = cluster.get_client()

with dask.config.set({"array.rechunk.method": "p2p", "optimization.fuse.active": False}):
rng = da.random.default_rng()
x = rng.random((100000, 100000))
x.rechunk((50000, 20)).rechunk((20, 50000)).sum().compute()
```

Logs:
```
distributed.scheduler - ERROR - Error transitioning "('rechunk-p2p-677393017a1df2b9929798754cba6a0e', 1, 2128)" from 'processing' to 'released'
Traceback (most recent call last):
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 1911, in _transition
recommendations, client_msgs, worker_msgs = func(
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 2563, in transition_processing_released
ws = self._exit_processing_common(ts)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 3178, in _exit_processing_common
self.check_idle_saturated(ws)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 2920, in check_idle_saturated
occ = ws.occupancy
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 820, in occupancy
return self._occupancy_cache or self.scheduler._calc_occupancy(
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 1856, in _calc_occupancy
assert occ >= 0, (res, network_occ, self.bandwidth)
AssertionError: (0.0, -4, 140927311.7922114)
```

because we do not properly release the task, this in turn seems to cause

```
Task exception was never retrieved
future: exception=AssertionError()>
Traceback (most recent call last):
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/core.py", line 924, in _handle_comm
result = await result
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/utils.py", line 754, in wrapper
return await func(*args, **kwargs)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 4303, in add_worker
await self.handle_worker(comm, address)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 5669, in handle_worker
await self.handle_stream(comm=comm, extra={"worker": worker})
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/core.py", line 1008, in handle_stream
handler(**merge(extra, msg))
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 5540, in handle_task_erred
self._transitions(recommendations, client_msgs, worker_msgs, stimulus_id)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 2015, in _transitions
new_recs, new_cmsgs, new_wmsgs = self._transition(key, finish, stimulus_id)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 1911, in _transition
recommendations, client_msgs, worker_msgs = func(
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 2563, in transition_processing_released
ws = self._exit_processing_common(ts)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/scheduler.py", line 3171, in _exit_processing_common
assert ws
AssertionError
```

and on the worker:

```
tornado.application - ERROR - Exception in callback functools.partial(>, exception=RuntimeError('Encountered invalid state')>)
Traceback (most recent call last):
File "/opt/coiled/env/lib/python3.10/site-packages/tornado/ioloop.py", line 740, in _run_callback
ret = callback()
File "/opt/coiled/env/lib/python3.10/site-packages/tornado/ioloop.py", line 764, in _discard_future_result
future.result()
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker.py", line 209, in wrapper
return await method(self, *args, **kwargs) # type: ignore
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker.py", line 1294, in handle_scheduler
await self.handle_stream(comm)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/core.py", line 1008, in handle_stream
handler(**merge(extra, msg))
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker.py", line 1909, in _
self.handle_stimulus(event)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker.py", line 222, in wrapper
return method(self, *args, **kwargs)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker.py", line 1924, in handle_stimulus
super().handle_stimulus(*stims)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker_state_machine.py", line 3718, in handle_stimulus
instructions = self.state.handle_stimulus(*stims)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker_state_machine.py", line 1360, in handle_stimulus
recs, instr = self._handle_event(stim)
File "/opt/coiled/env/lib/python3.10/functools.py", line 926, in _method
return method.__get__(obj, cls)(*args, **kwargs)
File "/opt/coiled/env/lib/python3.10/site-packages/distributed/worker_state_machine.py", line 2799, in _handle_remove_replicas
raise RuntimeError("Encountered invalid state") # pragma: no cover
```

XREF: #7538