Support stdlib zoneinfo.ZoneInfo (new in Python 3.10)

### Body

Python 3.10 introduced [`zoneinfo`](https://docs.python.org/3/library/zoneinfo.html) which covers usages of `pendulum.tz` (for Airflow uses, from what I can tell). Airflow should support `zoneinfo.ZoneInfo` for all places where it currently uses `pendulum.tz.Timezone`. This should be a good first step to phase out Pendulum from Airflow.

The module is also backported as [`backports.zoneinfo`](https://pypi.org/project/backports.zoneinfo/) to Python 3.6+, but it's probably not a priority to replace Pendulum usages with it for now.

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.

Start by locating Airflow usages of pendulum.tz.Timezone and compare their requirements with the zoneinfo.ZoneInfo documentation. Check the issue discussion for any current scope or constraints; done means the relevant timezone usages support ZoneInfo, with verification covering the affected behavior.

Written by the indexing model from the issue text.