Add readable enums

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

src/frostfs_testlib/testing/readable.py

@@ -1,4 +1,13 @@
 from abc import ABCMeta
+from enum import Enum
+
+
+class HumanReadableEnum(Enum):
+    def __str__(self):
+        return self._name_
+
+    def __repr__(self):
+        return self._name_
 
 
 class HumanReadableABCMeta(ABCMeta):