BUG: resampling empty series loses time zone from dtype

[MarcoGorelli]

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• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

df = pd.DataFrame({
    'ts': [],
    'values': []
}).astype({'ts': 'datetime64[ns, Atlantic/Faroe]'})
df.resample('2MS', on='ts', closed='left', label='left', origin='start')['values'].sum().index

Issue Description

this prints

DatetimeIndex([], dtype='datetime64[ns]', name='ts', freq='2MS')

Expected Behavior

DatetimeIndex([], dtype='datetime64[ns, Atlantic/Faroe]', name='ts', freq='2MS')

note that this works fine if the series isn't empty

In [27]: df = pd.DataFrame({
    ...:     'ts': [datetime(2020, 1, 1)],
    ...:     'values': [10]
    ...: })
    ...: df['ts'] = df['ts'].dt.tz_localize('Atlantic/Faroe')
    ...: df.resample('2MS', on='ts', closed='left', label='left', origin='start')['values'].sum().index
Out[27]: DatetimeIndex(['2020-01-01 00:00:00+00:00'], dtype='datetime64[ns, Atlantic/Faroe]', name='ts', freq='2MS')

Installed Versions

INSTALLED VERSIONS

commit : 965ceca
python : 3.10.6.final.0
python-bits : 64
OS : Linux
OS-release : 5.10.102.1-microsoft-standard-WSL2
Version : #1 SMP Wed Mar 2 00:30:59 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_GB.UTF-8
LOCALE : en_GB.UTF-8

pandas : 2.0.2
numpy : 1.24.3
pytz : 2023.3
dateutil : 2.8.2
setuptools : 67.6.1
pip : 23.0.1
Cython : None
pytest : 7.3.1
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.13.2
pandas_datareader: None
bs4 : 4.12.2
bottleneck : None
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.7.1
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 12.0.0
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None