### Description

ShutdownShardMigrationStatus serializes ShardAllocationDecision, which, as of #97803, is chunked. ShardAllocationDecision grows with the number of nodes. Therefore, it would save heap space to chunk ShutdownShardMigrationStatus as well.
x-pack/plugin/shutdown/src/main/java/org/elasticsearch/xpack/shutdown/GetShutdownStatusAction.java
for (SingleNodeShutdownStatus nodeShutdownStatus : shutdownStatuses) {
                    nodeShutdownStatus.toXContent(builder, params);
                }
                builder.endArray();
            }
            builder.endObject();
            return builder;
        }
        @Override
        public void writeTo(StreamOutput out) throws IOException {
            out.writeCollection(shutdownStatuses);
        }
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if ((o instanceof Response) == false) return false;
            Response response = (Response) o;
            return shutdownStatuses.equals(response.shutdownStatuses);
        }
        @Override
        public int hashCode() {
            return Objects.hash(shutdownStatuses);
        }
        @Override
        public String toString() {
            return Strings.toString(this);
        }
    }
}