BUG: Series.dt.tz accessor returns str instead of tzinfo when using PyArrow timestamps

[Giuzzilla]

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Reproducible Example

import pandas as pd
series = pd.Series(pd.to_datetime(["2023-04-05T00:00:00+00"]), dtype="timestamp[ns, tz=UTC][pyarrow]")
series.dt.tz

OUTPUT: 'UTC'

Issue Description

According to pandas documentation the dt.tz accessor of series should return the timezone as either datetime.tzinfo, pytz.tzinfo.BaseTZInfo, dateutil.tz.tz.tzfile, or None.

If you try to use this accessor on pyarrow-based timestamps, you'll get a str instead. str cannot be used with common datetime.datetime methods such as datetime.now(tz), which require a datetime.tzinfo.

Expected Behavior

import pandas as pd
series = pd.Series(pd.to_datetime(["2023-04-05T00:00:00+00"]), dtype="timestamp[ns, tz=UTC][pyarrow]")
series.dt.tz

EXPECTED OUTPUT: datetime.timezone.utc

Just like the following snippet on standard numpy-based datetimes:

import pandas as pd
series = pd.Series(pd.to_datetime(["2023-04-05T00:00:00+00"]))
series.dt.tz

Installed Versions

INSTALLED VERSIONS

commit : ba1cccd
python : 3.11.5.final.0
python-bits : 64
OS : Linux
OS-release : 5.14.0-1054-oem
Version : #61-Ubuntu SMP Fri Oct 14 13:05:50 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 2.1.0
numpy : 1.24.1
pytz : 2022.7
dateutil : 2.8.2
setuptools : 68.1.2
pip : 23.1.2
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : 1.1
pymysql : None
psycopg2 : 2.9.5
jinja2 : 3.1.2
IPython : 8.11.0
pandas_datareader : None
bs4 : 4.9.3
bottleneck : 1.3.7
dataframe-api-compat: None
fastparquet : None
fsspec : 2022.11.0
gcsfs : None
matplotlib : 3.7.1
numba : 0.57.1
numexpr : 2.8.5
odfpy : None
openpyxl : 3.0.9
pandas_gbq : None
pyarrow : 13.0.0
pyreadstat : None
pyxlsb : None
s3fs : 2022.11.0
scipy : 1.11.2
sqlalchemy : 1.4.49
tables : None
tabulate : None
xarray : None
xlrd : 1.2.0
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None