Document timezone semantics

[alamb]

Is your feature request related to a problem or challenge?

The automatic coercion and comparison rules for timestamps with timezones (especially how timestamps with None) are treated is not clear -- for example #10311 from @Abdullahsab3

Describe the solution you'd like

I would like something in the

Describe alternatives you've considered

No response

Additional context

No response

[alamb]

@tustvold do you know of any documentation in arrow-rs? I took a quick look and couldn't find anything

https://docs.rs/arrow/latest/arrow/?search=timezone

Possibly related: #5823 (comment)

[tustvold]

https://docs.rs/arrow-schema/latest/arrow_schema/enum.DataType.html#variant.Timestamp

On the variant for timestamp