Flexible restart write times (restart_fh)

[NickSzapiro-NOAA]

This PR enables writing forecast hour defined restarts ("restart_fh") in the same way as space-delimited floating point forecast hours in model_configure attributes, like restart_fh: 0.25 2.5 6 17 24. The current restart_fh in MOM6 is for integer forecast hours. This will allow CMEPS, MOM6, and CICE to have option of forecast hour restarts in addition to existing functionality. Restart writes are triggered when input restart_fh forecast hours are evenly divisible by a component's timestep (internally compared in units of integer seconds) and skipped otherwise.

Testing with cpld_control_gfsv17 confirms that restarts are b4b when (1) sharing common times with RESTART_N and (2) instead of RESTART_N. This feature is exercised in the datm_cdeps_gfs UFS regression test.

[NickSzapiro-NOAA]

Hi @jiandewang . May I ask if there is any feedback? This works in my testing

[jiandewang]

@NickSzapiro-NOAA I am out of office at this moment, will get back to you later

[jiandewang]

@NickSzapiro-NOAA let me ask NCAR folk for a look to make sure it won't have any negative impact on their side

[jiandewang]

@NickSzapiro-NOAA line 2109, 2126, 2119 and 2139 are too long, it won't pass MOM6 ci test. You need to use continuoue lines to split them.

[jiandewang]

@NickSzapiro-NOAA try to use force push to minimize commit log history (as suggested by MOM6 group)