REF: reshape.concat operate on arrays, not SingleBlockManagers
cc @TomAugspurger is there a better way to handle the assert_series_equal patch for the PandasArray tests?
> Can you explain the issue your change to assert_series_equal is working around?

Without the patched assert_series_equal, we get

```
_________________________________________________________________________ TestGetitem.test_loc_iloc_frame_single_dtype[object] _________________________________________________________________________

self = <pandas.tests.extension.test_numpy.TestGetitem object at 0x127f29f90>
data = <PandasArray>
[ (0,),  (1,),  (2,),  (3,),  (4,),  (5,),  (6,),  (7,),  (8,),  (9,), (10,),
 (11,), (12,), (13,), (14,...(87,),
 (88,), (89,), (90,), (91,), (92,), (93,), (94,), (95,), (96,), (97,), (98,),
 (99,)]
Length: 100, dtype: object

    def test_loc_iloc_frame_single_dtype(self, data):
        # GH#27110 bug in ExtensionBlock.iget caused df.iloc[n] to incorrectly
        #  return a scalar
        df = pd.DataFrame({"A": data})
        expected = pd.Series([data[2]], index=["A"], name=2, dtype=data.dtype)
    
        result = df.loc[2]
>       self.assert_series_equal(result, expected)

pandas/tests/extension/base/getitem.py:81: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

cls = <class 'pandas.tests.extension.test_numpy.TestGetitem'>, left = A    (2,)
Name: 2, dtype: object, right = A    (2,)
Name: 2, dtype: object, args = (), kwargs = {}

    @classmethod
    def assert_series_equal(cls, left, right, *args, **kwargs):
>       return tm.assert_series_equal(left, right, *args, **kwargs)
E       AssertionError: Attributes of Series are different
E       
E       Attribute "dtype" are different
E       [left]:  object
E       [right]: object

pandas/tests/extension/base/base.py:13: AssertionError
```

`test_loc_iloc_frame_single_dtype` is currently xfailed.  The edit to `PandasArray.astype` was because this had caused one of the cases of `test_loc_iloc_frame_single_dtype` to XPASS.  Removing the xfail led to 9 failures, 8 of which were fixed by the edit to `PandasArray.astype`.

I think the assert_series_equal issue has to do with the way we are patching `PandasArray._typ` in these tests, but i havent chased it down to be sure. Updated to just xfail more selectively and avoid patching assert_series_equal Can you check https://github.com/pandas-dev/pandas/pull/33125/files#r400169295?