Expose references to primitive inputs

[mkorbel1]

Motivation

For primitive modules like Swizzle and BusSubset, it would be nice to be able to easily find the inputs to those modules, especially while tracing around a hierarchy.

Desired solution

Expose references to inputs of base primitive modules to make parsing easier.

Alternatives considered

No response

Additional details

No response

[mkorbel1]

This also applies to inOuts. For example, BusSubset.subset doesn't actually point to the port.