Generated code fails to consider extern aliases

[AArnott]

Actual behavior

When generated code omits interop types because they are available via a metadata reference, references to those types are emitted assuming no extern alias applies. But in some more complex repos where multiple project references exist and types collide, the project may be using reference aliasing in order to disambiguate types in the various assemblies. In such a case, our generated code would need to prefix type references with the alias.

Expected behavior

Generated code should include an extern alias directive, and use that alias throughout the code whenever referencing the interop types from that assembly.
Where multiple metadata references include the same interop type, we'll have to pick one to use. This should probably come from the NativeMethods.json file.

Repro steps

See
CsWin32Sandbox_Repro.zip
for a repro.

Context

• CsWin32 version: 0.1.691-beta