Refactor for csharp bindings (#2331)

[Reptarsrage]

Rough draft for C# bindings refactor. Looking for feedback before adding unit tests, examples, docs and support for additional operating systems.

[Reptarsrage]

The greatest strength of this refactor is that the Bindings folder remains untouched after running gen_bindings.ps1. This means that no additional work is needed when updating lib bindings. We can just focus on maintaining the C# interop wrapper :)

[cebtenzzre]

I wouldn't normally be in favor of making such significant changes when the key problems with the binding are relatively small, but since it's been in need of a maintainer since last July and has been essentially unusable for a while, I say go for it :)

[mvenditto]

Few weekends ago I had a bit of free time so I started working to update the bindings to the latest iteration of the backend (+ fixing the NuGet package) as discussed here, but I'm already struggling to find time; so if someone who can contribute with more continuity wants to take over it would probably be beneficial for the project.

Talking about this PR, The changes are significant as it's almost a complete re-write and it takes a very different approach from mine so I'm not able to review this. I can eventually help for troubleshooting here and there if needed.

I'm sorry but sadly I cannot keep up with side projects as I would like to.

[Reptarsrage]

Alrighty just wanted to get this out asap and get some feedback to make sure i wasn't wasting my time. Sounds like I can put a little more elbow grease into this project. I'll get to work and update this PR as I go 👍🏻