GFSv16 production: add logfile write functionality to indicate gridded output is complete

[MatthewMasarik-NOAA]

Is your feature request related to a problem? Please describe.
During GFSv16 production runs a rare issue has been seen when the wave gridded post script attempts to access an output file before it has finished writing.

Describe the solution you'd like
Modify WW3 gridded output to write logfiles indicating the output file (for each grid and forecast hour) has finished writing. The gridded post script will then be able to check for this file, and only proceed with reading the gridded output if the logfile is present.

Describe alternatives you've considered
This is the option that has been collectively agreed on.

Additional context
See Production Update issue in global-workflow: NOAA-EMC/global-workflow#3094