Resolve ambiguity for permanent timezone changes

[eugeneius]

Biz::Time already passes true as the dst parameter to local_to_utc to avoid the ambiguity of converting a local time that occurred twice due to daylight savings time.

However if a local time occurs twice due to a permanent timezone change, the dst parameter doesn't help. local_to_utc can be given a block to handle this case:

https://github.com/tzinfo/tzinfo/blob/v2.0.6/lib/tzinfo/timezone.rb#L613-L619

The dst parameter will not be able to resolve an ambiguity resulting from the clocks being set back without changing from daylight savings time to standard time. In this case, if a block is specified, it will be called to resolve the ambiguity. The block must take a single parameter - an Array of {TimezonePeriod}s that need to be resolved. The block can select and return a single {TimezonePeriod} or return nil or an empty Array to cause an {AmbiguousTime} exception to be raised.

I encountered this problem due to a recent timezone change in Kazakhstan: https://mm.icann.org/pipermail/tz-announce/2024-February/000081.html

I used an older example in the test so that it doesn't require the latest tz database.