[3.12] gh-114440: Close writer pipe in multiprocessing.Queue, not concurrent.futures (GH-114489)

This was left out of the 3.12 backport for three related issues:
- gh-107219 (which adds `self.call_queue._writer.close()` to `_ExecutorManagerThread` in `concurrent.futures`)
- gh-109370 (which changes this to be only called on Windows)
- gh-109047 (which moves the call to `multiprocessing.Queue`'s `_terminate_broken`)

Without this change, ProcessPoolExecutor sometimes hangs on Windows
when a worker process is terminated.

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Lib/multiprocessing/queues.py

@@ -164,6 +164,11 @@ class Queue(object):
         # gh-94777: Prevent queue writing to a pipe which is no longer read.
         self._reader.close()
 
+        # gh-107219: Close the connection writer which can unblock
+        # Queue._feed() if it was stuck in send_bytes().
+        if sys.platform == 'win32':
+            self._writer.close()
+
         self.close()
         self.join_thread()