Currently, `TransportGetShutdownStatusAction` is executed in a transport thread, this action can do a substantial amount of work (O(# shards) in some cases) in the transport thread preventing pending transport tasks to make progress and potentially causing cluster instability. This action should be dispatched into a different thread pool to avoid such issues.
x-pack/plugin/shutdown/src/test/java/org/elasticsearch/xpack/shutdown/TransportGetShutdownStatusActionTests.java
ClusterState state = ClusterState.builder(ClusterState.EMPTY_STATE)
            .metadata(
                Metadata.builder()
                    .indices(Map.of())
                    .putCustom(
                        NodesShutdownMetadata.TYPE,
                        new NodesShutdownMetadata(
                            Map.of(
                                bogusNodeId,
                                SingleNodeShutdownMetadata.builder()
                                    .setType(SingleNodeShutdownMetadata.Type.REMOVE)
                                    .setStartedAtMillis(randomNonNegativeLong())
                                    .setReason(this.getTestName())
                                    .setNodeId(bogusNodeId)
                                    .build()
                            )
                        )
                    )
            )
            .nodes(
                DiscoveryNodes.builder()
                    .add(
                        DiscoveryNode.createLocal(
                            Settings.builder()
                                .put(Settings.builder().build())
                                .put(Node.NODE_NAME_SETTING.getKey(), SHUTTING_DOWN_NODE_ID)
                                .build(),
                            new TransportAddress(TransportAddress.META_ADDRESS, 9200),
                            SHUTTING_DOWN_NODE_ID
                        )