ENH: 将 `str.get_dummies()` 的默认 dtype 更改为 bool,以保持与 `pd.get_dummies()` 的一致性

The following compares the results of using `pd.get_dummies()` and `str.get_dummies()` on Series with various dtypes. Only when the `dtype` is `string[pyarrow]` do the results match, while in all other cases, the output types differ.