Release and rebootstrap pipeline cannot find msft artifacts

[ellahathaway]

Related to #5244

BlobArtifacts is no longer being published by the unified-build pipeline. This breaks the release and rebootstrap pipelines the pipelines look for the msft artifact in BlobArtifacts.

The msft artifacts can now be found in the <buildname>_Artifacts container. More specifically, we can also find the artifact path and names in the AssetManifests/MergedManifest.xml artifact:

<Blob Id="Sdk/<version>/dotnet-sdk-<version>-linux-x64.tar.gz" DotNetReleaseShipping="true" PipelineArtifactName="AzureLinux_x64_Cross_x64_Artifacts" PipelineArtifactPath="assets/Release/Sdk/<version>/dotnet-sdk-<version>-linux-x64.tar.gz" RepoOrigin="sdk" Visibility="External"/>

This is a regression from dotnet/dotnet#935.

[ellahathaway]

Completed in https://dev.azure.com/dnceng/internal/_git/dotnet-release/pullrequest/50892