Revert "pythongh-118761: Improve import time of subprocess (pythonGH-129427)"

This reverts commit 49f2465.

This caused bugs in the `__del__` finalizer:
 python#118761 (comment)

Author: gpshead

Lib/subprocess.py

@@ -43,8 +43,10 @@
 import builtins
 import errno
 import io
+import locale
 import os
 import time
+import signal
 import sys
 import threading
 import warnings
@@ -142,8 +144,6 @@ def __init__(self, returncode, cmd, output=None, stderr=None):
 
     def __str__(self):
         if self.returncode and self.returncode < 0:
-            # Lazy import to improve module import time
-            import signal
             try:
                 return "Command '%s' died with %r." % (
                         self.cmd, signal.Signals(-self.returncode))
@@ -381,8 +381,6 @@ def _text_encoding():
     if sys.flags.utf8_mode:
         return "utf-8"
     else:
-        # Lazy import to improve module import time
-        import locale
         return locale.getencoding()
 
 
@@ -1665,9 +1663,6 @@ def send_signal(self, sig):
             # Don't signal a process that we know has already died.
             if self.returncode is not None:
                 return
-
-            # Lazy import to improve module import time
-            import signal
             if sig == signal.SIGTERM:
                 self.terminate()
             elif sig == signal.CTRL_C_EVENT:
@@ -1769,9 +1764,6 @@ def _posix_spawn(self, args, executable, env, restore_signals, close_fds,
             """Execute program using os.posix_spawn()."""
             kwargs = {}
             if restore_signals:
-                # Lazy import to improve module import time
-                import signal
-
                 # See _Py_RestoreSignals() in Python/pylifecycle.c
                 sigset = []
                 for signame in ('SIGPIPE', 'SIGXFZ', 'SIGXFSZ'):
@@ -2221,13 +2213,9 @@ def send_signal(self, sig):
         def terminate(self):
             """Terminate the process with SIGTERM
             """
-            # Lazy import to improve module import time
-            import signal
             self.send_signal(signal.SIGTERM)
 
         def kill(self):
             """Kill the process with SIGKILL
             """
-            # Lazy import to improve module import time
-            import signal
             self.send_signal(signal.SIGKILL)