Push runtime artifacts nupkgs to GitHub packages of this repo

[driver1998]

SourceBuilt.Artifacts contains the .NET runtime, apphost, AOT/C2R related packages for linux-(musl-)loongarch64, would be useful to push these on a NuGet package repo somewhere, like what Loongson does with their old-world release.

That way, building .NET apps targeting LoongArch can be much easier, without hacks like https://driver1998.github.io/posts/dotnet-cross-publish-loongarch/.

IIRC GitHub packages is available in any GitHub repo, and can host NuGet packages, so this can be a great option.

https://docs.github.com/zh/packages/working-with-a-github-packages-registry/working-with-the-nuget-registry

[driver1998]

Pushing everything in the artifacts tar would be too risky as it might clash with the same packages from NuGet.org, but the following should be a safe subset:

Microsoft.NETCore.App.Crossgen2.linux-loongarch64
Microsoft.NETCore.App.Host.linux-loongarch64
Microsoft.NETCore.App.Runtime.linux-loongarch64
Microsoft.AspNetCore.App.Runtime.linux-loongarch64
runtime.linux-loongarch64.Microsoft.DotNet.ILCompiler
runtime.linux-loongarch64.Microsoft.NETCore.DotNetAppHost
runtime.linux-loongarch64.Microsoft.NETCore.ILAsm
runtime.linux-loongarch64.Microsoft.NETCore.ILDAsm
runtime.linux-loongarch64.Microsoft.NETCore.TestHost

Too bad we can't just push these to NuGet.org directly (Microsoft reserved the corresponding package name prefixes).