Fork TransportRollupCapsAction to MANAGEMENT POOL (#89803)

We can't run these actions on the transport threads in their current form.
The fully deserialize the mapping for each index they inspect which will
take a massive amount of time if either a large number of indices or a large
number of fields (indices * fields_per_index) overall are inspected.

docs/changelog/89803.yaml

@@ -0,0 +1,5 @@
+pr: 89803
+summary: Fork `TransportRollupCapsAction` to MANAGEMENT POOL
+area: Rollup
+type: bug
+issues: []

x-pack/plugin/rollup/src/main/java/org/elasticsearch/xpack/rollup/action/TransportGetRollupCapsAction.java

@@ -15,6 +15,7 @@ import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.tasks.Task;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xpack.core.rollup.action.GetRollupCapsAction;
 import org.elasticsearch.xpack.core.rollup.action.RollableIndexCaps;
@@ -33,7 +34,7 @@ public class TransportGetRollupCapsAction extends HandledTransportAction<GetRoll
 
     @Inject
     public TransportGetRollupCapsAction(TransportService transportService, ClusterService clusterService, ActionFilters actionFilters) {
-        super(GetRollupCapsAction.NAME, transportService, actionFilters, GetRollupCapsAction.Request::new);
+        super(GetRollupCapsAction.NAME, transportService, actionFilters, GetRollupCapsAction.Request::new, ThreadPool.Names.MANAGEMENT);
         this.clusterService = clusterService;
     }
 

x-pack/plugin/rollup/src/main/java/org/elasticsearch/xpack/rollup/action/TransportGetRollupIndexCapsAction.java

@@ -14,6 +14,7 @@ import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.tasks.Task;
+import org.elasticsearch.threadpool.ThreadPool;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xpack.core.rollup.action.GetRollupIndexCapsAction;
 import org.elasticsearch.xpack.core.rollup.action.RollableIndexCaps;
@@ -40,7 +41,13 @@ public class TransportGetRollupIndexCapsAction extends HandledTransportAction<
         ActionFilters actionFilters,
         IndexNameExpressionResolver indexNameExpressionResolver
     ) {
-        super(GetRollupIndexCapsAction.NAME, transportService, actionFilters, GetRollupIndexCapsAction.Request::new);
+        super(
+            GetRollupIndexCapsAction.NAME,
+            transportService,
+            actionFilters,
+            GetRollupIndexCapsAction.Request::new,
+            ThreadPool.Names.MANAGEMENT
+        );
         this.clusterService = clusterService;
         this.resolver = indexNameExpressionResolver;
     }