Fix couple build issues related to authoring scenarios

[manodasanW]

This PR addresses a couple issues related to authoring scenarios:

• If an authoring project had project references to other C# projects, those projects got treated as also implementing the winmd of the authoring project which isn't true. Instead, it should be the authoring project dll is the one that implements the winmd and the others are just copied over. This addresses that by no longer looping over all the managed dlls but they are still added for publishing.
• When an authoring project is consumed by a native project, any managed dependencies are copied over. But if there were multiple references to the same dll due to different versions such as with WinRT.Runtime where a version can come from the nuget reference and the other from the Windows SDK projection, they were not correctly resolved to choose the higher version. We are now using ResolveAssemblyReferences to resolve those issues so that way we do not need to handle them ourselves.
• Also noticed after the changes that project reference dependencies were not getting copied over, so checking for CopyLocal also while copying them.

Tested with a couple different project reference scenarios to ensure things work as expected.