get_timezone_location does not work with python's ZoneInfo object

[youtux]

get_timezone_location does not render correctly the ZoneInfo objects. These are part of python as of python 3.9 (and available as backport).

MCVE:
$ pip install backports.zoneinfo babel

# tz.py
from babel.dates import get_timezone_location
from backports import zoneinfo
import pytz

ams_native = zoneinfo.ZoneInfo("Europe/Amsterdam")
ams_pytz = pytz.timezone("Europe/Amsterdam")

print(get_timezone_location(ams_pytz))  # output: "Netherlands Time"
print(get_timezone_location(ams_native))  #  output: "Unknown Region (CEST) Time"

Python version: 3.6.11
babel version: 2.8.0

I think this can be easily fixed by checking the timezone.key attribute. Shall I make a PR?

[akx]

Please do! :)