Fix and Re-expose Passthrough API which is currently it is blocked by IL2CPP fails to properly map interface methods

This is regarding a bug reported by Microsoft on the Unity IL2CPP team.

Doc with description of the issue and details:

[Internal link]{}

 

Repro: Download ComInterfaceRepro.zip and build an run an IL2CPP Windows player

Expected: App shows the unity.com homepage

Actual: App crashes

Reproducible: 6000.0.17f1 Windows