TST/BUG: pyarrow test fixtures upcasting dtypes
There are a few test fixtures in `test_arrow.py` that create an array from a subset of another array using `ArrowExtensionArray._from_sequence`. They are not passing the dtype which results in upcasting for smaller dtypes.

```
import pandas as pd

dtype = "int32[pyarrow]"

arr = pd.array([1, 2, 3], dtype=dtype)
arr2 = type(arr)._from_sequence([arr[0], arr[1]])

print(arr2.dtype)  # -> int64[pyarrow]
```
Thanks @lukemanley 