BUG: Series(pyarrow-backed).round raising AttributeError

[lukemanley]

• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/v2.0.0.rst file if fixing a bug or adding a new feature.

Adding ArrowExtensionArray.round to fix the following:

import pandas as pd

pd.Series([1.23], dtype="float64[pyarrow]").round(1)

# AttributeError: 'ArrowExtensionArray' object has no attribute 'round'

[mroeschke]

Thanks @lukemanley