Clean up clusters between tests (#41187)

This PR adds additional cleanup when stopping the node.
The data dir is excepted because it gets reused in some tests.
Without this cleanup the number of working dir copies could grew to
exhaust all available disk space.

Author: alpar-t

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

@@ -884,6 +884,8 @@ 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)))
             }
         }
     }