Be more intelligent about creation of overflow/underflow/saturate signals

[amykyta3]

When a counter is created, it will unconditionally create internal overflow/underflow/incrsaturate/decrsaturate entries in the field combo structure, and assign them.

Since these are unused, they can create coverage review noise.

Be more intelligent about the creation of these, and only emit if actually necessary.
During the design scanning phase, scan for references to these RHS properties.