Fix blocking code in AirNow sensor

[kamiyo]

Proposed change

Fixed warning of blocking in AirNow sensor creation (because of a ZoneInfo call). This was actually not doing anything because AirNow returns timezones as three-letter abbreviations (i.e. CST), but ZoneInfo only works with IANA strings (i.e. "America/Chicago") because the three-letter abbreviations are non-unique. AirNow is a US based service, so the three-letter works for it, but there isn't a good way of parsing the three-letter ones, I don't think.

So, my solution is just to treat the time of observation as a string with the three-letter zone, and not bother with actually parsing the time into an actual datetime object.

I also added the state to the reporting station sensor.

In a future PR, should we think about moving more things to sensors? Dev docs say to avoid using extra_attributes for things that change (like the category and category level in this case, perhaps even observation time).

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• Dependency upgrade
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Additional information

• This PR fixes or closes issue: fixes airnow integration does blocking I/O in the event loop to import modules #116860
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[home-assistant]

Hey there @asymworks, mind taking a look at this pull request as it has been labeled with an integration (airnow) you are listed as a code owner for? Thanks!

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[samip5]

LGTM

[bdraco]

I started adding a new async helper in #117721 that can be used for cases where we want to load uncached ZoneInfo in the event loop

[bdraco]

Another option would be to use https://dateutil.readthedocs.io/en/stable/parser.html but it might need to parse in the executor