cocotb Remove unnecessary objects from VPI discovery

Closes #3353.

Need investigation into whether the following should also be removed.

[x] vpiGate
[x] vpiPort
[x] vpiPrimTerm
[x] vpiRefObj

Jul 06 '23 14:07 ktbarrett

Perhaps we need to add a case where we expect the type, but throw the object away because we know it isn't valuable?

Jul 06 '23 19:07 ktbarrett

Apparently there is a test to see if we can find a SV gate, but I'm not sure yet finding gates is even useful, so I'm testing to see if the input and output "ports" can be found.

Jul 18 '23 13:07 ktbarrett

We can't see any signals under a gate object, so their discovery is not important. The access_gate test will be removed.

Jul 18 '23 18:07 ktbarrett

This is actually a bigger PITA than expected. Our "expected don't cares" are still passed back up to the GPI layer as NULLs, which get encoded as GPI_NOT_NATIVE objects, causing an error. This occurs when iterators over hierarchies are done.

Jul 19 '23 17:07 ktbarrett

The discovery tests are now not finding certain objects. Investigation is needed to find out what's now missing after removing objects from iteration.

Sep 04 '23 22:09 ktbarrett

Rerunning CI.

Apr 27 '24 13:04 ktbarrett