FPrime GDS does not gracefully handle files downlinks of the same filename

[rrieber]

Say an FPrime spacecraft downlinks filename.bin, then downlinks the same file a second time for redundancy. The current behavior of FPrime GDS would be to overwrite the first filename.bin with the second. If there were undetected corruption or other issues, those would be permanently imprinted on the final version of the file.

Let's explore another scenario. Say an FPrime spacecraft downlinks image.bin. Then deletes it, makes a new image.bin and downlinks that. FPrime GDS would do the same thing, it would overwrite the first version of image.bin with the second version if image.bin.

Note that both of these operational scenarios are used all the time. I'm not talking once per mission, I'm talking multiple times per day.

I think FPrime GDS should be modified to ensure received files all have unique names. I've seen them appended with the Earth Received Time (ERT) with great success. It's easy to remove with a simple RegEx and ensures uniqueness.

See also #2458 for a mildly-related issue.