`send_task_state_to_scheduler` may not need `self.data[key]`

Currently in [`Worker.send_task_state_to_scheduler(...)`]( https://github.com/dask/distributed/blob/f2f82c6c2e8d36731cb3fb82fb1f80ea0323358e/distributed/worker.py#L1837 ), we check [`self.data[key]` or `self.actors[key]`]( https://github.com/dask/distributed/blob/f2f82c6c2e8d36731cb3fb82fb1f80ea0323358e/distributed/worker.py#L1839-L1842 ) and then determine relevant metadata about that key like its [`nbytes` and `typ`]( https://github.com/dask/distributed/blob/f2f82c6c2e8d36731cb3fb82fb1f80ea0323358e/distributed/worker.py#L1843-L1844 ). While the code appears to handle [access of `self.nbytes` with a fallback to using `value`]( https://github.com/dask/distributed/blob/f2f82c6c2e8d36731cb3fb82fb1f80ea0323358e/distributed/worker.py#L1843 ), the access pattern using `__getitem__`, which would raise a `KeyError` if the `key` wasn't there. This makes one wonder if that fallback to get `value` is even needed here.

For context, this came up in this discussion ( https://github.com/dask/distributed/pull/3628#pullrequestreview-379910338 ).