* Copy eng\common from Arcade repo.
* Enable Spark to build using dotnet/arcade
* Update coverlet version to work around bug in older version.
* Fix up test directory lookup for new artifacts location.
* Don't use dummy versions for local dev builds.
* Fix up official build for new output artifacts location
* Rearrange official build
- Set official build id parameter
- Build nuget package on Build leg
- Publish the worker using MSBuild instead of cmd
* Ensure only our .nupkg gets signed and copied, and the .nupkg is placed directly in the Packages folder.
Clean up official build definition.
Eric Erhardt