CF_UnionArgs_Payload_t elements dword and hword not used, union not necessary

[skliper]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I reviewed the CF README.md file to see if the feature is in the major future work.
• I performed a cursory search to see if the feature request is relevant, not redundant, nor in conflict with other tickets.

Is your feature request related to a problem? Please describe.
dword and hword are not used in the CF_UnionArgs_Payload_t union, only byte:

CF/fsw/src/cf_msg.h

Lines 159 to 169 in 0774746

	/* unionargs -
	*
	* A lot of commands have a single byte arg, and the old application had 3 spare bytes after that.
	*
	* So this structure gives the flexibility of a single byte arg, 2 halfwords, or a dword, all in one declaration. */
	typedef union CF_UnionArgs_Payload
	{
	uint32 dword;
	uint16 hword[2];
	uint8 byte[4];
	} CF_UnionArgs_Payload_t;

Describe the solution you'd like
Remove unnecessary union

Describe alternatives you've considered
CF_UnionArgsCmd_t is somewhat out of family in that it specifies unnecessary payload elements for some of the commands. The only common benefit seems to be byte 0 which is channel, supporting all channels generically with 255. Consider untangling all the layers of abstraction and go back to simple command processing.

Additional context
None

Requester Info
Jacob Hageman - NASA/GSFC

[chillfig]

Initial PR solving this issue is reverted by #395. Reopening to be considered for Equuleus-rc2.