Create nuspec for OpenCL

[jasoncouture]

Depends on #487 - Adds a NuGet package for OpenCL (CLBLAST)

[martindevans]

Looks good, I'll check it again in detail once #487 is merged.

[martindevans]

Can this be rebased onto master and squashed into one commit, since some of the changes have been done in other PRs.

Before doing that please remove libllama.so and llama.dll (those binaries will be added when #479 is merged).

Also please link exactly where clblast.dll and libclblast.so came from, so file hashes can be verified.

[jasoncouture]

clblast.dll source: "https://github.com/CNugteren/CLBlast/releases/download/1.6.0/CLBlast-1.6.0-windows-x64.7z"

After some discussion on slack, we're going to yank the SO out for now, for a few reasons.

1. It's relatively easy to install for your distro.
2. you need opencl installed anyway, installing libclblast will pull that in for you automatically.
3. OpenCL on linux has 3 or 4 variants, a generic version, intel, amd, nvidia. So, since that needs to be installed, may as well leave it to the user to also install libclblast as well.

On windows, however, OpenCL is normally packaged with the graphics driver. So we can validate the dll and it should "just work".

[jasoncouture]

Updated and squashed to a single commit.

[martindevans]

Thanks! I'll merge this and start a new compile run

[martindevans]

@jasoncouture looks like the run failed: https://github.com/SciSharp/LLamaSharp/actions/runs/7790112762/workflow