[release/6.0] Update to latest

- SDK and runtimes
- baselines
  - started w/ <https://dev.azure.com/dnceng/_apis/resources/Containers/8590413/BlobArtifacts?itemPath=BlobArtifacts%2FMergedManifest.xml>
- re-enable baseline validation
- check in 6.0.0 files for later targeting packs
  - extracted from <https://www.nuget.org/packages/Microsoft.AspNetCore.App.Ref/6.0.0>