Script for building package variants

[nathanrw]

Provided a script for building Arch in multiple variants.

• Added presets to .sln and .csproj for the different variants
• Fixed the build for non-PURE_ECS benchmarks.
• Added script Build.sh to build the different presets
  • The script fiddles the .csproj file before building to tweak the .nupkg name based on the preset. Perhaps
    someone more familiar with dotnet could suggest a better way of doing this.
  • The script can upload packages if you pass it --publish and provide your API key. I have not tested
    this.
• Added a script Test.sh to test the various presets
• Called the new scripts in workflow.

[genaray]

Could you probably demonstrate the usage? ^^
I saw there's a usage in the build.sh. But one small example would be great :)

[nathanrw]

Usage should be

./scripts/Build.sh

to build. Followed by

./scripts/Build.sh --publish --api-key yourApiKey

to publish. But I haven't tested the publishing!