Fix #75, Use size_t for size variables/parameters + zero-out the gloabl data struct

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution

• Fixes Size variables/parameters could be updated to use the size_t type #75
  • Converts suitable variables + function parameters that represent size to the size_t type
  • Zero's out the global data struct at the beginning of initialization
  • A couple of minor fixes are added here including typos and replacing some function name text to use __func__ (to avoid potential future technical debt)

Testing performed
GitHub CI actions all passing successfully (incl. Build + Run, Unit/Functional Tests etc.).

System(s) tested on
Debian GNU/Linux 12 (bookworm)
Current main branch of cFS bundle.

Contributor Info
Avi Weiss   @thnkslprpt