A few size variables could be updated to size_t or CF_ChunkSize_t

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I performed a cursory search to see if the bug report is relevant, not redundant, nor in conflict with other tickets.

Describe the bug
A few variables in CF could be updated to the more expressive size_t or CF_ChunkSize_t types

Code snips
val should be of CF_ChunkSize_t type:

CF/fsw/src/cf_cmd.h

Line 475 in 0f18ae4

CFE_Status_t CF_CmdValidateChunkSize(uint32 val, uint8 chan_num);

size should be of size_t type:

CF/fsw/src/cf_cmd.c

Lines 942 to 947 in 0f18ae4

	struct
	{
	void * ptr;
	uint32 size;
	int (*fn)(uint32, uint8 chan_num);
	} item;

...and few others.

Expected behavior
Update where appropriate

Reporter Info
Avi Weiss @thnkslprpt