add LocalOffset type that stores the timezone name

[esheppa]

This could also be implemented as an extra field on FixedOffset, which would mean it would no longer be a breaking change, but in that case it would make the FixedOffset type more than three times larger.

This should fix #749 on unix platforms. We would need to capture timezone name on Windows as well, potentially from here hence why this is in draft status for now

[pamburus]

Hi, what stops this pull request from being fixed and merged?

[pitdicker]

We would need to capture timezone name on Windows as well, potentially from here hence why this is in draft status for now

The TIME_ZONE_INFORMATION structure doesn't seem to play along. The documentation says it returns names such as "EST" and "PDT", but in reality it returns full, localized names instead. We would need some other source.

Edit: StandardName and DaylightName are localized, TimeZoneKeyName has a full, unlocalized name.

[pitdicker]

Closing this PR for now because realistically there have been enough changes that it is easier to start fresh. #1563 tracks adding a LocalOffset type.

@esheppa Thank you for your work here!