Use `size_t` for size parameters/variables

[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/parameters representing size could be updated to the more expressive size_t typedef.

Code snips
DataLength should be size_t:

DS/fsw/src/ds_file.h

Lines 121 to 127 in 2a6c6a2

	* \param[in] FileIndex Destination file index
	* \param[in] FileData Pointer to packet data
	* \param[in] DataLength Length of packet data
	*
	* \sa #DS_AppFileStatus_t, #DS_DestFileEntry_t
	*/
	void DS_FileWriteData(int32 FileIndex, const void *FileData, uint32 DataLength);

MaxFileSize should be size_t:

DS/fsw/src/ds_table.h

Lines 353 to 357 in 2a6c6a2

	* \param[in] MaxFileSize Maximum Size Limit value
	*
	* \sa #DS_TableVerifyAge, #DS_TableVerifyCount, #DS_DestFileEntry_t
	*/
	bool DS_TableVerifySize(uint32 MaxFileSize);

...and a few other local variables.

Expected behavior
Update to size_t where possible.

Reporter Info
Avi Weiss @thnkslprpt