Use packed data within ChineseBasedYearInfo (#4465)

Part of #3933

This does not yet add data loading, but it gets very close to it.

This PR makes the size of Date not bloat too much, without requiring
much computation for any of the getters -- they're all basic bit
operations.

components/calendar/src/chinese.rs

@@ -228,64 +228,7 @@ impl Calendar for Chinese {
     /// leap months. For example, in a year where an intercalary month is added after the second
     /// month, the month codes for ordinal months 1, 2, 3, 4, 5 would be "M01", "M02", "M02L", "M03", "M04".
     fn month(&self, date: &Self::DateInner) -> types::FormattableMonth {
-        let ordinal = date.0 .0.month;
-        let leap_month_option = date.0 .0.year_info.leap_month;
-        let leap_month = if let Some(leap) = leap_month_option {
-            leap.get()
-        } else {
-            14
-        };
-        let code_inner = if leap_month == ordinal {
-            // Month cannot be 1 because a year cannot have a leap month before the first actual month,
-            // and the maximum num of months ina leap year is 13.
-            debug_assert!((2..=13).contains(&ordinal));
-            match ordinal {
-                2 => tinystr!(4, "M01L"),
-                3 => tinystr!(4, "M02L"),
-                4 => tinystr!(4, "M03L"),
-                5 => tinystr!(4, "M04L"),
-                6 => tinystr!(4, "M05L"),
-                7 => tinystr!(4, "M06L"),
-                8 => tinystr!(4, "M07L"),
-                9 => tinystr!(4, "M08L"),
-                10 => tinystr!(4, "M09L"),
-                11 => tinystr!(4, "M10L"),
-                12 => tinystr!(4, "M11L"),
-                13 => tinystr!(4, "M12L"),
-                _ => tinystr!(4, "und"),
-            }
-        } else {
-            let mut adjusted_ordinal = ordinal;
-            if ordinal > leap_month {
-                // Before adjusting for leap month, if ordinal > leap_month,
-                // the month cannot be 1 because this implies the leap month is < 1, which is impossible;
-                // cannot be 2 because that implies the leap month is = 1, which is impossible,
-                // and cannot be more than 13 because max number of months in a year is 13.
-                debug_assert!((2..=13).contains(&ordinal));
-                adjusted_ordinal -= 1;
-            }
-            debug_assert!((1..=12).contains(&adjusted_ordinal));
-            match adjusted_ordinal {
-                1 => tinystr!(4, "M01"),
-                2 => tinystr!(4, "M02"),
-                3 => tinystr!(4, "M03"),
-                4 => tinystr!(4, "M04"),
-                5 => tinystr!(4, "M05"),
-                6 => tinystr!(4, "M06"),
-                7 => tinystr!(4, "M07"),
-                8 => tinystr!(4, "M08"),
-                9 => tinystr!(4, "M09"),
-                10 => tinystr!(4, "M10"),
-                11 => tinystr!(4, "M11"),
-                12 => tinystr!(4, "M12"),
-                _ => tinystr!(4, "und"),
-            }
-        };
-        let code = types::MonthCode(code_inner);
-        types::FormattableMonth {
-            ordinal: ordinal as u32,
-            code,
-        }
+        date.0.month()
     }
 
     /// The calendar-specific day-of-month represented by `date`
@@ -297,13 +240,11 @@ impl Calendar for Chinese {
     fn day_of_year_info(&self, date: &Self::DateInner) -> types::DayOfYearInfo {
         let prev_year = date.0 .0.year.saturating_sub(1);
         let next_year = date.0 .0.year.saturating_add(1);
-        // TODO(#3933): we should maybe have this cached already
-        let prev_info = self.get_precomputed_data().load_or_compute_info(prev_year);
         types::DayOfYearInfo {
             day_of_year: date.0.day_of_year(),
             days_in_year: date.0.days_in_year_inner(),
             prev_year: Self::format_chinese_year(prev_year, None),
-            days_in_prev_year: Self::days_in_provided_year(prev_year, prev_info),
+            days_in_prev_year: date.0.days_in_prev_year(),
             next_year: Self::format_chinese_year(next_year, None),
         }
     }
@@ -402,8 +343,9 @@ impl<A: AsCalendar<Calendar = Chinese>> DateTime<A> {
     }
 }
 
+type ChineseCB = calendrical_calculations::chinese_based::Chinese;
 impl ChineseBasedWithDataLoading for Chinese {
-    type CB = calendrical_calculations::chinese_based::Chinese;
+    type CB = ChineseCB;
     fn get_precomputed_data(&self) -> ChineseBasedPrecomputedData<Self::CB> {
         Default::default()
     }
@@ -426,7 +368,7 @@ impl Chinese {
         let cyclic = (number - 1).rem_euclid(60) as u8;
         let cyclic = NonZeroU8::new(cyclic + 1); // 1-indexed
         let rata_die_in_year = if let Some(info) = year_info_option {
-            info.new_year
+            info.new_year::<ChineseCB>(year)
         } else {
             Inner::fixed_mid_year_from_year(number)
         };
@@ -692,7 +634,7 @@ mod test {
             let iso = Date::try_new_iso_date(year, 6, 1).unwrap();
             let chinese_date = iso.to_calendar(Chinese);
             assert!(chinese_date.is_in_leap_year());
-            let new_year = chinese_date.inner.0 .0.year_info.new_year;
+            let new_year = chinese_date.inner.0.new_year();
             assert_eq!(
                 expected_month,
                 calendrical_calculations::chinese_based::get_leap_month_from_new_year::<