Add repr and str for most classes used in parametrize

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

src/frostfs_testlib/utils/converting_utils.py

@@ -1,10 +1,23 @@
 import base64
 import binascii
 import json
+from typing import Tuple
 
 import base58
 
 
+def calc_unit(value: float, skip_units: int = 0) -> Tuple[float, str]:
+    units = ["B", "KiB", "MiB", "GiB", "TiB"]
+
+    for unit in units[skip_units:]:
+        if value < 1024:
+            return value, unit
+
+        value = value / 1024.0
+
+    return value, unit
+
+
 def str_to_ascii_hex(input: str) -> str:
     b = binascii.hexlify(input.encode())
     return str(b)[2:-1]