ESQL: Fix writing for LOOKUP status (elastic#119296) (elastic#119320)

This fixes writing the `status` of the LOOKUP operator. It just wasn't
registered.

Closes elastic#119086

Author: nik9000

docs/changelog/119296.yaml

@@ -0,0 +1,6 @@
+pr: 119296
+summary: Fix writing for LOOKUP status
+area: ES|QL
+type: bug
+issues:
+ - 119086

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plugin/EsqlPlugin.java

@@ -61,6 +61,7 @@
 import org.elasticsearch.xpack.esql.action.RestEsqlGetAsyncResultAction;
 import org.elasticsearch.xpack.esql.action.RestEsqlQueryAction;
 import org.elasticsearch.xpack.esql.enrich.EnrichLookupOperator;
+import org.elasticsearch.xpack.esql.enrich.LookupFromIndexOperator;
 import org.elasticsearch.xpack.esql.execution.PlanExecutor;
 import org.elasticsearch.xpack.esql.expression.ExpressionWritables;
 import org.elasticsearch.xpack.esql.plan.PlanWritables;
@@ -192,6 +193,7 @@ public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
         entries.add(SingleValueQuery.ENTRY);
         entries.add(AsyncOperator.Status.ENTRY);
         entries.add(EnrichLookupOperator.Status.ENTRY);
+        entries.add(LookupFromIndexOperator.Status.ENTRY);
 
         entries.addAll(BlockWritables.getNamedWriteables());
         entries.addAll(ExpressionWritables.getNamedWriteables());