Decrease merge task checker periodicity in tests (elastic#130082)

Decreases the periodicity (from 5s to 100ms), for some tests, with which merge tasks are checked if there's sufficient available disk space to execute or if they've been aborted since enqueued for execution.

Fixes elastic#130044

Author: albertzaharovits

muted-tests.yml

@@ -563,9 +563,6 @@ tests:
   issue: https://github.com/elastic/elasticsearch/issues/130010
 - class: org.elasticsearch.xpack.esql.qa.mixed.MixedClusterEsqlSpecIT
   issue: https://github.com/elastic/elasticsearch/issues/128224
-- class: org.elasticsearch.xpack.autoscaling.storage.ReactiveStorageIT
-  method: testScaleDuringSplitOrClone
-  issue: https://github.com/elastic/elasticsearch/issues/130044
 - class: org.elasticsearch.cluster.metadata.ComposableIndexTemplateTests
   method: testMergeEmptyMappingsIntoTemplateWithNonEmptySettings
   issue: https://github.com/elastic/elasticsearch/issues/130050

x-pack/plugin/autoscaling/src/internalClusterTest/java/org/elasticsearch/xpack/autoscaling/storage/AutoscalingStorageIntegTestCase.java

@@ -14,6 +14,7 @@
 import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.datastreams.DataStreamsPlugin;
+import org.elasticsearch.index.engine.ThreadPoolMergeExecutorService;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.xpack.autoscaling.LocalStateAutoscaling;
 import org.elasticsearch.xpack.autoscaling.action.GetAutoscalingCapacityAction;
@@ -39,7 +40,10 @@ protected Settings nodeSettings(final int nodeOrdinal, final Settings otherSetti
         builder.put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_LOW_DISK_WATERMARK_SETTING.getKey(), LOW_WATERMARK_BYTES + "b")
             .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_HIGH_DISK_WATERMARK_SETTING.getKey(), HIGH_WATERMARK_BYTES + "b")
             .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_DISK_FLOOD_STAGE_WATERMARK_SETTING.getKey(), "0b")
-            .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_REROUTE_INTERVAL_SETTING.getKey(), "0ms");
+            .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_REROUTE_INTERVAL_SETTING.getKey(), "0ms")
+            // the periodicity for the checker for the available disk space as well as the merge tasks' aborting status
+            // the default of 5 seconds might timeout some tests
+            .put(ThreadPoolMergeExecutorService.INDICES_MERGE_DISK_CHECK_INTERVAL_SETTING.getKey(), "100ms");
         return builder.build();
     }