Use size_t for variables/parameters representing size

[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
Some variables/parameters in cFE representing size could be updated to the more expressive size_t typedef.

Most cases are already uint32 and are assigned values from other size_t types or sent into functions expecting size_t parameters anyway.

Expected behavior
Update to size_t where appropriate.

Reporter Info
Avi Weiss @thnkslprpt