Making it easy to use NuGet package caching in github workflows

[LegalizeAdulthood]

I was running into a lot of problems trying to get NuGet package caching to work properly in my workflows.

After going through a bunch of debugging sessions, I resolved all the problems and figured out how to get things working for my public repositories. There are a bunch of moving pieces and policies that can interfere with proper operation and debugging them is non-obvious.

I've created two github actions that make your life simpler:

• LegalizeAdulthood/vcpkg-github-cache is the main action that configures your workflow to use github NuGet packages as cached vcpkg dependencies
• This main action is also available as LegalizeAdulthood/vcpkg-github-cache/setup if you prefer a more explicit name for the setup step.
• A secondary action LegalizeAdulthood/vcpkg-github-cache/analyze is available to analyze problems with package caching. The most common situation is likely to be that you're sharing packages across multiple public repositories and the packages must be manually configured to allow multiple repositories to update the packages. Unfortunately there's no way to manipulate package permissions through the gh CLI, REST API or GraphQL API. The action will provide a summary table with links to make it easier for you to configure package permissions as needed.

I've tested this out on my public repositories and it seems to be working well. Finally, using cached packages is easy!