Function calendrical_calculations::chinese_based::get_leap_month_from_new_year

pub fn get_leap_month_from_new_year<C: ChineseBased>(new_year: RataDie) -> u8

Given that new_year is the first day of a leap year, find which month in the year is a leap month. Since the first month in which there are no major solar terms is a leap month, this function cycles through months until it finds the leap month, then returns the number of that month. This function assumes the date passed in is in a leap year and tests to ensure this is the case in debug mode by asserting that no more than thirteen months are analyzed.

Conceptually similar to code from Calendrical Calculations by Reingold & Dershowitz Lisp reference code: https://github.com/EdReingold/calendar-code2/blob/main/calendar.l#L5443-L5450