.item() breaks on dataarray if dask arrays are (implicitely) used

What happened?

When using .item() to get a value (for example of a calculated average via .mean()) of an dataarray, this results in an error if the underlying array is a dask array.

What did you expect to happen?

I did not explicitely use dask, therefore I expected .item() to work. If dask arrays can be used implicitely, then I would expect the API to work, regardless of the underlying array data type.

Minimal Complete Verifiable Example

import xarray as xr

ds = xr.tutorial.open_dataset("air_temperature", chunks="auto")  # force dask usage but this can also happen implicitly

ds.air.mean().item()

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.

Relevant log output

Traceback (most recent call last):
  File "/home/tschmitt/.cache/pypoetry/virtualenvs/xr-bug-ugHUypuW-py3.9/lib/python3.9/site-packages/xarray/core/ops.py", line 191, in _call_possibly_missing_method
    method = getattr(arg, name)
AttributeError: 'Array' object has no attribute 'item'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/tschmitt/software/xr_bug/mwe.py", line 6, in <module>
    ds.air.mean().item()
  File "/home/tschmitt/.cache/pypoetry/virtualenvs/xr-bug-ugHUypuW-py3.9/lib/python3.9/site-packages/xarray/core/ops.py", line 203, in func
    return _call_possibly_missing_method(self.data, name, args, kwargs)
  File "/home/tschmitt/.cache/pypoetry/virtualenvs/xr-bug-ugHUypuW-py3.9/lib/python3.9/site-packages/xarray/core/ops.py", line 193, in _call_possibly_missing_method
    duck_array_ops.fail_on_dask_array_input(arg, func_name=name)
  File "/home/tschmitt/.cache/pypoetry/virtualenvs/xr-bug-ugHUypuW-py3.9/lib/python3.9/site-packages/xarray/core/duck_array_ops.py", line 77, in fail_on_dask_array_input
    raise NotImplementedError(msg % func_name)
NotImplementedError: 'item' is not yet a valid method on dask arrays
Exception ignored in: <function CachingFileManager.__del__ at 0x7f8da8e1b1f0>
Traceback (most recent call last):
  File "/home/tschmitt/.cache/pypoetry/virtualenvs/xr-bug-ugHUypuW-py3.9/lib/python3.9/site-packages/xarray/backends/file_manager.py", line 246, in __del__
TypeError: 'NoneType' object is not callable

Anything else we need to know?

No response

Environment

Start with the reproducible example using xarray.tutorial.open_dataset(..., chunks="auto") and trace the failure through xarray/core/ops.py, especially _call_possibly_missing_method, and duck_array_ops.py. Confirm the expected behavior for .item() on a dask-backed mean and add coverage showing that the minimal example completes successfully.