Add convenience function for long running

PiperOrigin-RevId: 843424475

Author: hubatish

perfkitbenchmarker/app_service.py

@@ -307,6 +307,12 @@ def GetLifeCycleMetrics(self):
       s.metadata.update(self.metadata)
     return self.samples
 
+  def IsAppLongRunning(self) -> bool:
+    """Returns true if the app is long running."""
+    if not self.builder:
+      return False
+    return self.builder.IsAppLongRunning()
+
   def _PostCreate(self):
     """Method called after _CreateResource."""
     if self.builder: