[#318] Add tombstone expiration test

Signed-off-by: a.berezin <a.berezin@yadro.com>

src/frostfs_testlib/hosting/interfaces.py

@@ -117,6 +117,17 @@ class Host(ABC):
             service_name: Name of the service to stop.
         """
 
+    @abstractmethod
+    def send_signal_to_service(self, service_name: str, signal: str) -> None:
+        """Send signal to service with specified name using kill -<signal>
+
+        The service must be hosted on this host.
+
+        Args:
+            service_name: Name of the service to stop.
+            signal: signal name. See kill -l to all names
+        """
+
     @abstractmethod
     def mask_service(self, service_name: str) -> None:
         """Prevent the service from start by any activity by masking it.