Refactor release pipeline

[tpwalke2]

CI/CD pipeline currently creates a draft Github release then publishes to NuGet.

However, when a new release is published in Github, the build runs again.

Update the CI/CD pipeline to

• create a draft release in GitHub and upload built nupkg
• react to tags being published
  • skip if not release tag
  • skip building/test for release tags
  • find the published release (on Github)
  • download the nupkg from the release and upload to Nuget