Update build, analyzers to match core Autofac

[tillig]

• Change build to GitHub Actions. This means new Autofac.Extensions.DependencyInjection packages will be published in GitHub Packages rather than on MyGet.
• Switch to use the central .github folder for the organization instead of one-off versions in the repo.
• Update analyzer rules to match core Autofac.
• Fix analyzer issues due to new rules.

[tillig]

Some Googling says the commit/build status is cached. You can't remove the previous failed check. I'm going to just let it go through.