Implement MPMD parallel copies in *_out functions of forecast_postdet.sh

[DavidHuber-NOAA]

Description

This implements MPMD to copy forecast files back to COM at the end of the fcst and efcs jobs in dev/gfs.v17.

Type of change

• Bug fix (fixes something broken)
• New feature (adds functionality)
• Maintenance (code refactor, clean-up, new CI test, etc.)

Change characteristics

• Is this change expected to change outputs NO
• Is this a breaking change (a change in existing functionality)? NO
• Does this change require a documentation update? NO
• Does this change require an update to any of the following submodules? NO

How has this been tested?

Will be tested in a high-res parallel on WCOSS2.

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have documented my code, including function, input, and output descriptions
• My changes generate no new warnings
• New and existing tests pass with my changes
• This change is covered by an existing CI test or a new one has been added

[DavidHuber-NOAA]

FYI @JessicaMeixner-NOAA @CatherineThomas-NOAA @RuiyuSun. I will run this through a high res cycle to get timings.