Unsurprisingly, the only thing affected by this was the `import-helper`
tests. These have lost all of the results relating to `ImportMember`s,
but apart from that the underlying behaviour should be the same.
I also limited the test to only `CfgNode`s, as a bunch of `EssaNode`s
suddenly appeared when I switched to API graphs.
Finally, I used `API::moduleImport` with a dotted name in the type
tracking tests. This goes against the API graphs interface, but I think
it's more correct for this use case, as these type trackers are doing
the "module attribute lookup" bit manually.
