Run cleanup jobs sequentially instead of in parallel

Each cleanup job try to use all available processors.
Running them in parallel will only increase the amount
of context switching without utilizing more processors.

community/index/src/main/java/org/neo4j/index/internal/gbptree/GroupingRecoveryCleanupWorkCollector.java

@@ -57,11 +57,7 @@ public void add( CleanupJob job )
     @Override
     public void start() throws Throwable
     {
-        CleanupJob job;
-        while ( (job = jobs.poll()) != null )
-        {
-            jobScheduler.schedule( recoveryCleanup, job );
-        }
+        jobScheduler.schedule( recoveryCleanup, allJobs() );
     }
 
     @Override
@@ -73,4 +69,16 @@ public void stop() throws Throwable
     public void shutdown() throws Throwable
     {   // no-op
     }
+
+    private Runnable allJobs()
+    {
+        return () ->
+        {
+            CleanupJob job;
+            while ( (job = jobs.poll()) != null )
+            {
+                job.run();
+            }
+        };
+    }
 }