Re-bootstrap pipeline uses .final MSFT artifact despite non-stable version input

[ellahathaway]

See dotnet/dotnet#1742

When running the re-bootstrap pipeline using a non-stable build as input, the pipeline unexpectedly picked up the .final version of the msft SDK. This occurs even though the provided input should not result in a .final artifact.

• This appears to be caused by the pipeline logic: it uses the msft commit to acquire the latest successful build from the msft pipeline, pulling the SDK artifact from there.
• The last successful msft build for the msft commit is 2762988, not the expected 2761553.

We should adjust the re-bootstrap logic to pull the msft pipeline run a different way. Using the bar build ID might be an option.

[ellahathaway]

PR: https://dev.azure.com/dnceng/internal/_git/dotnet-release/pullrequest/52074