Move shared code to testlib

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

src/frostfs_testlib/reporter/interfaces.py

@@ -1,6 +1,6 @@
 from abc import ABC, abstractmethod
 from contextlib import AbstractContextManager
-from typing import Any
+from typing import Any, Callable
 
 
 class ReporterHandler(ABC):
@@ -17,6 +17,17 @@ class ReporterHandler(ABC):
             Step context.
         """
 
+    @abstractmethod
+    def step_decorator(self, name: str) -> Callable:
+        """A step decorator from reporter.
+
+        Args:
+            name: Name of the step.
+
+        Returns:
+            decorator for the step
+        """
+
     @abstractmethod
     def attach(self, content: Any, file_name: str) -> None:
         """Attach specified content with given file name to the test report.