ice_calendar: fix yearly output with 'histfreq_n /= 1'

In ice_calendar::calendar, we loop over the output frequencies and set
'write_history(ns)' to true if the current time corresponds to the
frequency requested in 'histfreq_n'. For yearly outputs, however, the
model year 'myear' is used in the modulo computation, whereas it's
really the number of elapsed years since the beginning of the run that
should be used. This has been the case since the update of the time
manager in b720380 (Update Time Manager (CICE-Consortium#566), 2021-03-16). Prior to
that, the variable 'nyr' was used, which at that point of the subroutine
contained the number of years since the beginning of the run.

Fix that regression by introducing the variable 'elapsed_years'.

cicecore/shared/ice_calendar.F90

@@ -328,6 +328,7 @@ subroutine calendar()
       integer (kind=int_kind) :: &
          ns                         , & ! loop index
          yearp,monthp,dayp,hourp    , & ! previous year, month, day, hour
+         elapsed_years              , & ! since beginning this run
          elapsed_days               , & ! since beginning this run
          elapsed_months             , & ! since beginning this run
          elapsed_hours                  ! since beginning this run
@@ -350,7 +351,8 @@ subroutine calendar()
       idate = (myear)*10000 + mmonth*100 + mday ! date (yyyymmdd) 
       yday = daycal(mmonth) + mday            ! day of the year
       hour = (msec+1)/(seconds_per_hour)
-      elapsed_months = (myear - year_init)*months_per_year + mmonth - month_init
+      elapsed_years = myear - year_init
+      elapsed_months = elapsed_years*months_per_year + mmonth - month_init
       elapsed_days = compute_days_between(year_init,month_init,day_init,myear,mmonth,mday)
       elapsed_hours = elapsed_days * hours_per_day
       call calendar_date2time(myear,mmonth,mday,msec,timesecs)
@@ -373,7 +375,7 @@ subroutine calendar()
          select case (histfreq(ns))
          case ("y", "Y")
             if (new_year  .and. histfreq_n(ns)/=0) then
-               if (mod(myear, histfreq_n(ns))==0) &
+               if (mod(elapsed_years, histfreq_n(ns))==0) &
                    write_history(ns) = .true.
             endif
          case ("m", "M")