Create fixed buffer struct for cleaner C style arrays

[Lucas Girouard-Stranks]

Proposed here: https://github.com/dotnet/csharplang/blob/a3d67d141501101af9dbb9e8192ca8b4c717e316/proposals/fixed-sized-buffers.md

It's possible to simply to generate the C# code which would be functionally the same as the proposed solution in the above link