Operations between DataFrame and ExtensionArray loses EA dtype
What's the expected behavior here?

```python
In [9]: a = pd.array([1, None, 2, 3], dtype='Int64')

In [10]: df = pd.DataFrame([[1, 2, 3, 4]])

In [11]: (a + df).dtypes
Out[11]:
0      int64
1    float64
2      int64
3      int64
dtype: object
```

Would we expect the eventual op to dispatch to the ExtensionArray, preserving the Int64Dtype for each?

I believe this is different from https://github.com/pandas-dev/pandas/issues/28506