CF "cf_field.h" macro cleanup

[jphickey]

This issue was imported from the GSFC issue tracking system

Imported from: [GSFCCFS-1802] CF "cf_field.h" macro cleanup
Originally submitted by: Hickey, Joseph P. (GSFC-582.0)[VANTAGE SYSTEMS INC] on Wed Nov 17 11:13:49 2021

Original Description:
The "cf_field.h" defines a macro called "inc_subfield" .... thankfully this appears to not be used anywhere. Recommend removal.

The other macros "FIELD_SET_VAL" and "FIELD_GET_VAL" have a couple recommended cleanups:

1.They are multi-line/complex macros. Recommend to convert to inline functions instead - they only operate on "uint8" base values so this should not be a problem.
2. They are then aliased to a shorthand "FSV" and "FGV", respectively. It appears the author simply didn't want to write the long names? Is there a real justification for having the same macro/function under two names? Only the shorthand is actually used in the code. Recommend to choose one name and use it.

[jphickey]

After PR #137 is merged, this consolidates use of fields to only the Encode/Decode routines.

Recommendation is to further move FSV/FGV and the related field info into the codec file (removing it from cf_cfdp_pdu.h). This will more appropriately scope this info, and fix the remaining issues here. Nothing outside of cf_codec.c should care about these bit fields.