Support discontinuous time ranges

Chronify time configs currently only support a single, continuous time range. We will likely need to support discontinuous ranges in dsgrid. An example is where a modeled dataset will have multiple weather years and model years. Suppose that model years are 2030, 2040, 2050 and weather years are 2012, 2018, and 2024. Chronify will ultimately have to check time consistency on the resulting dataset. Each of the the three model years will have the time ranges 2012-01-01 - 2012-12-31, 2018-01-01 - 2018-12-31, and 2024-01-01 - 2024-12-31.

We could change the current data models to allow multiple ranges or make a new data model that includes instances of the existing models, like this:

class ListTimeRange(TimeBaseModel):

    ranges: list[DatetimeRange] | list[AnnualTimeRange] | list[IndexTimeRange] | list[RepresentativePeriodTime]