SDK5: Restore caching for ModelInfo.ModelInspector while fixing type conflicts

[andrzejskowronski]

Re-revert the #3260 from #3374 changes, but to do that we need to make sure at the very least we notify the user when the ModelInspector will attempt to import a type from another satellite assembly.
We don't have a solid reproduction sample yet, but it can easily happen if stu3::Patient gets ToTypedElement with PocoElementNode, while it gets passed r4::ModelInfo.ModelInspector.
Likewise it can probably happen with poco serialization somewhere.
So we should make it a general safety change in the ModelInspector.ImportType logic.

We should also consider that sometimes this might be a valid case in Simplifier context, where the resource in r4 might refer to a STU3 resource.

[ewoutkramer]

Yes, that's exactly it. Thanks again @PaulDeac for helping us diagnose.