Document how to change CFE_TIME_Print() timestamp format

[CDKnightNASA]

Is your feature request related to a problem? Please describe.
Some missions may want to use a different timestamp format for event messages on the console (such as "MET" or "DD HH:MM:SS" or whatnot.) A proposal to use strftime made the logic more complex and did have a measurable performance impact, so instead I suggest documenting how a mission would change the format and cautioning against using a strftime or sprintf formatting. I suggest the comment be added to the CFE_TIME_Print() definition in cfe_time.h.

Describe the solution you'd like
See description above. Comment in cfe_time.h.

Describe alternatives you've considered
Do nothing. Add comment to cfe_time_api.c. Add sample code in comments. Whatnot.

Additional context
See related, withdrawn PR #2370

Requester Info
Christopher.D.Knight@nasa.gov