This started with implementing TemporalMonthDayString. It turns out that
the facilities needed to parse that production includes nearly all the
helpers to parse each of:
TemporalDateTimeString
TemporalInstantString
TemporalMonthDayString
TemporalTimeString
TemporalYearMonthString
TemporalZonedDateTimeString
As most of these invoke the same helpers with different options. So,
all 6 of those productions are implemented here.