dotnet: load assembly via RuntimeAssembly.nLoadImage

source: https://dr4k0nia.github.io/posts/NixImports-a-NET-loader-using-HInvoke/#the-runtime

The sample that I found references this method via:

```
Assembly.GetExecutingAssembly().GetType().GetMethod("nLoadImage", BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.InvokeMethod)
```