Centralize Scriptorium input source policy across config, analyze, and previous-cache

internal/previouscache/previouscache.go

@@ -229,7 +229,11 @@ func artifactRelativePathCandidates(
 		candidates = append(candidates, normalized)
 	}
 
+	sourceDescriptor, err := artifactpolicy.PreviousSessionSourceDescriptorForConfiguredKey(artifactName)
 	sourceID := artifactpolicy.ConfiguredSourceID(artifactName)
+	if err == nil {
+		sourceID = sourceDescriptor.ConfiguredSourceID
+	}
 	if rel, ok := manifestArtifactRelativePathBySourceID(previousManifest, sourceID); ok {
 		appendCandidate(rel)
 		base := path.Base(rel)