Pass $BUILDKITE_AGENT_META_DATA_QUEUE to pipeline.yml

Reimplement keeping the queue value for subsequent steps. This requires Agent 3.0 to be stable. This reverts commit ac3ea61.

Author: ticky

.buildkite/pipeline.yml

@@ -2,3 +2,5 @@ steps:
   - name: ":hammer: Example Script"
     command: "script.sh"
     artifact_paths: "artifacts/*"
+    agents:
+      queue: "${BUILDKITE_AGENT_META_DATA_QUEUE:-default}"