Revert "Clean up clusters between tests (#41187)"

This reverts commit 44a0c468cf.

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

@@ -964,8 +964,6 @@ class ClusterFormationTasks {
             }
             doLast {
                 project.delete(node.pidFile)
-                // Large tests can exhaust disk space, clean up on stop, but leave the data dir as some tests reuse it
-                project.delete(project.fileTree(node.baseDir).minus(project.fileTree(node.dataDir)))
             }
         }
     }