How to build Open3D to be able to wrap the DLL for a .NET project?

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [ ] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### My Question

I'm trying to compile Open3D to get a DLL which I can use in C++ project which exports methods that I can use in a .NET C# project via P/Invoke.

I have tried hints from #2889 and #5608, or whatever I could find on StackOverflow. Information is sparse.

I managed to build a DLL that I can use in a C++ console application that I created in Visual Studio but not in a project that is compiled to a DLL containing `__declspec(dllexport)`.

As soon as I include Open3D.h my build fails with errors from various Open3D header files. I only have .NET/C# background so I don't know why it's even trying to build these files.

I'm only using the Windows runtime and I have tried to compile `main` and `0.18.0`. The `0.18.0` build fails and/or the `INSTALL` target doesn't work as expected.

Do you have any information on this?

Start by reviewing the approaches referenced in issues #2889 and #5608, then inspect the Windows build configuration and the failing 0.18.0 INSTALL target. Done would be a documented, reproducible build path for producing a DLL usable from a C# project via P/Invoke, including the relevant Windows runtime steps.

Written by the indexing model from the issue text.