Should I be able to initialise a Series with a pandas array and pandas dtype?
#### Code Sample, a copy-pastable example if possible

```python
>>> import pandas as pd
>>> from pandas.core.arrays import PandasDtype
>>> pd.Series(pd.array([1,2,3]), dtype=PandasDtype('int64'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/marco/pandas/pandas/core/series.py", line 323, in __init__
    data = sanitize_array(data, index, dtype, copy, raise_cast_failure=True)
  File "/home/marco/pandas/pandas/core/construction.py", line 431, in sanitize_array
    subarr = subarr.astype(dtype, copy=copy)
  File "/home/marco/pandas/pandas/core/arrays/integer.py", line 475, in astype
    data = self.to_numpy(dtype=dtype, **kwargs)
  File "/home/marco/pandas/pandas/core/arrays/masked.py", line 144, in to_numpy
    data = self._data.astype(dtype, copy=copy)
TypeError: data type not understood
```

#### Output of ``pd.show_versions()``

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<details>


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</details>
