Revert "[lit] cleanup unused imports" (#144054)

Reverts llvm/llvm-project#143930 as it causes build failures:
llvm/llvm-project#143930 (comment)

Author: charles-zablit

lit/LitConfig.py

@@ -1,12 +1,14 @@
 from __future__ import absolute_import
-
 import inspect
 import os
+import platform
 import sys
 
+import lit.Test
+import lit.formats
+import lit.TestingConfig
 import lit.util
 
-
 # LitConfig must be a new style class for properties to work
 class LitConfig(object):
     """LitConfig - Configuration data for a 'lit' test runner instance, shared

lit/TestRunner.py

@@ -1,4 +1,7 @@
 from __future__ import absolute_import
+import errno
+import io
+import itertools
 import getopt
 import os, signal, subprocess, sys
 import re
@@ -9,8 +12,11 @@
 import shutil
 import tempfile
 import threading
+import typing
 from typing import Optional, Tuple
 
+import io
+
 try:
     from StringIO import StringIO
 except ImportError:

lit/discovery.py

@@ -6,8 +6,8 @@
 import os
 import sys
 
-from lit import Test, util
 from lit.TestingConfig import TestingConfig
+from lit import LitConfig, Test, util
 
 
 def chooseConfigFileFromDir(dir, config_names):

lit/worker.py

@@ -12,6 +12,8 @@
 import traceback
 
 import lit.Test
+import lit.util
+
 
 _lit_config = None
 _parallelism_semaphores = None