gh-118761: Revert "Improve import time of subprocess (GH-129427)" (#130201)

* Revert "gh-118761: Improve import time of `subprocess` (GH-129427)"

This reverts commit 49f24650e4.
Also known as f502c8f6a6db4be27c97a0e5466383d117859b7f in 3.13 (PR #129447)
Also known as f65aa0d1bf7b636ab8f9d226429205854b24cd7a in 3.12 (PR #129448)

This caused bugs in the `__del__` finalizer:
 https://github.com/python/cpython/issues/118761#issuecomment-2661504264

---------

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Lib/subprocess.py

@@ -43,8 +43,10 @@ getstatusoutput(...): Runs a command in the shell, waits for it to complete,
 import builtins
 import errno
 import io
+import locale
 import os
 import time
+import signal
 import sys
 import threading
 import warnings
@@ -142,8 +144,6 @@ class CalledProcessError(SubprocessError):
 
     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 @@ class Popen:
             # 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 @@ class Popen:
             """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 @@ class Popen:
         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)