Attempt to improve upload performance (distributed-system-analysis#3501)

Use subprocess tar command to extract files from tarball

PBENCH-1226

lib/pbench/server/__init__.py

@@ -5,6 +5,7 @@
 from datetime import datetime, timedelta, tzinfo
 from enum import auto, Enum
 from logging import Logger
+import os
 from pathlib import Path
 from time import time as _time
 from typing import Dict, List, Optional, Union
@@ -21,6 +22,10 @@
 JSONOBJECT = Dict[JSONSTRING, JSONVALUE]
 JSON = JSONVALUE
 
+# Define a type hint for "Path-like" parameters, so the cumbersomeness of the
+# type won't discourage us from using it where it is warranted.
+PathLike = Union[str, bytes, os.PathLike]
+
 
 class OperationCode(Enum):
     """Enumeration for CRUD operations.