Emit embedded or inlined structs in Go to correspond with struct unifications in schemas

[sdboyer]

The Go code generator does not currently handle struct unifications correctly. Rather than either inlining or embedding the type, it simply omits it entirely.

The initial fix here should should embed the type, without any option for inlining. If a use case presents itself, we can add a separate config option to enable inlining later.

This case is covered by the testdata/lineage/unifyref.txtar, and will impact (among probably many others) the Azure Monitor plugin in grafana

[joanlopez]

Assigning it to @spinillos cause she already started some work 🎉 ➡️ #154

[joanlopez]

Hey @spinillos, @sdboyer,
I see the aforementioned PR has been merged, and indeed the lineage/unifyref case was removed from the ToDo list there. So, can we close this issue? Or is there any other work still remaining?
Thanks!