Stop Executing SLM Policy Transport Action on Snapshot Pool (#45727)

* Executing SLM policies on the snapshot thread will block until a snapshot finishes if the pool is completely busy executing that snapshot
* Fixes #45594

x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/slm/action/TransportExecuteSnapshotLifecycleAction.java

@@ -52,7 +52,7 @@ public class TransportExecuteSnapshotLifecycleAction
     }
     @Override
     protected String executor() {
-        return ThreadPool.Names.SNAPSHOT;
+        return ThreadPool.Names.GENERIC;
     }
 
     @Override