re-bootstrap pipeline calculates the Microsoft.DotNet.Arcade.Sdk version and SHA incorrectly

[ViktorHofer]

https://dev.azure.com/dnceng/internal/_git/dotnet-release?path=/eng/pipeline/source-build-release/steps/re-bootstrap.yml

The input source for these versions is the source-manifest.json file. That one points to the SHA and package version produced by the Arcade repository. There are several issues with that:

• The version points to the Arcade published by the standalone Arcade repository's official build but a re-bootstrap should use the Arcade from the VMR. Otherwise changes will lag behind until the Arcade official build has all the required backflow updates.
• The packageVersion metadata will go away soon (together with the git-info files)
• We want the outgoing not the incoming version of Arcade, the version that's inside the PSB artifacts.
• The SHA should be a dotnet/dotnet SHA

Noticed in dotnet/dotnet#591

The VerticalManifest.xml which is part of the artifacts payload should probably used to find any produced version (Arcade & .NET SDK).

[ellahathaway]

Closed with https://dev.azure.com/dnceng/internal/_git/dotnet-release/pullrequest/50291