Fix blocking I/O in the event loop when loading timezones

[bdraco]

Breaking change

Constructing ZoneInfo objects may do blocking I/O to load the zone info from disk if the timezone passed is not in the cache.

dt_util.async_get_time_zone is now available to replace dt_util.get_time_zone to fetch a time zone in the event loop which is async safe and will not do blocking I/O in the event loop.

hass.config.set_time_zone is deprecated and replaced with hass.config.async_set_time_zone. hass.config.set_time_zone will be removed in 2025.6. Setting the time zone only affects tests, as no integration should be calling this function in production.

Examining dt_util.DEFAULT_TIME_ZONE directly is deprecated and dt_util.get_default_time_zone() should be used instead.

If your integration needs to construct ZoneInfo objects in the event loop, it is recommended to use the aiozoneinfo library.

Proposed change

aiozoneinfo is a simple wrapper that check if the ZoneInfo is in the cache, and if not it will load it in the executor since ZoneInfo will do blocking I/O in the loop if the zone info is not in the cache https://github.com/python/cpython/blob/a3db4e8f964499eabeddb19a6201f3d3b73d7443/Lib/zoneinfo/_zoneinfo.py#L73. A new library was created because integrations have the same problem and will likely want to use it in their PyPI package.

We have this problem in a few different places in the code. To avoid solving it multiple different ways, dt_util.async_get_time_zone is now available.

Everything that used dt_util.DEFAULT_TIME_ZONE, manually constructed the zone info, or used dt_util.get_time_zone(entity.hass.config.time_zone) has been updated to dt_util.get_default_time_zone()

All instances in core that did blocking I/O to load the time zone data from disk have been fixed except for airnow which needs a more involved solution, see #117615

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue: airnow integration does blocking I/O in the event loop to import modules #116860
• Link to documentation pull request: Handling time zones without blocking the event loop blog post developers.home-assistant#2174

Checklist

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[bdraco]

draft because all the current usage needs to be analyzed to see what its going to take to move to the new method as some of these calls are not in coros

[frenck]

LGTM, thanks @bdraco 👍

../Frenck

[bdraco]

thanks