We now avoid the old `IModuleReference` interface which required allocating for every type being resolved.
Instead `MetadataModule.ResolveModule` now combines decoding+resolving assembly references into a single step.
This allows the type system to maintain a cache indexed by row number.
This also changes the behavior of resolving references within a compilation: We now prefer an exact match (name + version + publickeytoken) first; and fall back to a name-only match only if no exact match exists.
This somewhat improves the decompilation of assemblies created by using ilmerge to combine assemblies with different target frameworks.
While support for multi-module assemblies isn't fully working yet; it is clear at this point that we want
to treat each module in a multi-module assembly separately for the purposes of the type system.
This is a work-in-progress; ILSpy is not functional with this commit.
The old code path still exists but is broken because some classes were modified for the new system.
The new system is still highly incomplete (types only have fields, but no methods).
Daniel Grunwald