fix: stop thread pools when an error occurs during startup

Signed-off-by: Gerard de Leeuw <gdeleeuw@leeuwit.nl>

Author: lion7

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/Operator.java

@@ -203,7 +203,12 @@ public synchronized void start() {
   public void stop() throws OperatorException {
     Duration reconciliationTerminationTimeout =
         configurationService.reconciliationTerminationTimeout();
+
     if (!started) {
+      // Always stop the executor service manager to prevent dangling threads,
+      // even if the operator didn't fully start
+      configurationService.getExecutorServiceManager().stop(reconciliationTerminationTimeout);
+
       return;
     }
     log.info(