Turn off real-mem breaker in REST tests

With this commit we disable the real-memory circuit breaker in REST
tests as this breaker is based on real memory usage over which we have
no (full) control in tests and the REST client is not yet ready to retry
on circuit breaker exceptions.

This is only meant as a temporary measure to avoid spurious test
failures while we ensure that the REST client can handle those
situations appropriately.

Closes #32050
Relates #31767
Relates #31986 
Relates #32074

buildSrc/src/main/groovy/org/elasticsearch/gradle/test/ClusterFormationTasks.groovy

@@ -331,6 +331,12 @@ class ClusterFormationTasks {
         }
         // increase script compilation limit since tests can rapid-fire script compilations
         esConfig['script.max_compilations_rate'] = '2048/1m'
+        // Temporarily disable the real memory usage circuit breaker. It depends on real memory usage which we have no full control
+        // over and the REST client will not retry on circuit breaking exceptions yet (see #31986 for details). Once the REST client
+        // can retry on circuit breaking exceptions, we can revert again to the default configuration.
+        if (node.nodeVersion.major >= 7) {
+            esConfig['indices.breaker.total.use_real_memory'] = false
+        }
         esConfig.putAll(node.config.settings)
 
         Task writeConfig = project.tasks.create(name: name, type: DefaultTask, dependsOn: setup)