gh-98703: Add tests for closing _ProactorSocketTransport with proactor event loop (GH-98730)

(cherry picked from commit 96ae80f)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

Author: miss-islington

Lib/test/test_asyncio/test_proactor_events.py

@@ -296,6 +296,27 @@ def test_force_close_idempotent(self):
         # and waiters will never be notified leading to hang.
         self.assertTrue(self.protocol.connection_lost.called)
 
+    def test_force_close_protocol_connection_lost_once(self):
+        tr = self.socket_transport()
+        self.assertFalse(self.protocol.connection_lost.called)
+        tr._closing = True
+        # Calling _force_close twice should not call
+        # protocol.connection_lost twice
+        tr._force_close(None)
+        tr._force_close(None)
+        test_utils.run_briefly(self.loop)
+        self.assertEqual(1, self.protocol.connection_lost.call_count)
+
+    def test_close_protocol_connection_lost_once(self):
+        tr = self.socket_transport()
+        self.assertFalse(self.protocol.connection_lost.called)
+        # Calling close twice should not call
+        # protocol.connection_lost twice
+        tr.close()
+        tr.close()
+        test_utils.run_briefly(self.loop)
+        self.assertEqual(1, self.protocol.connection_lost.call_count)
+
     def test_fatal_error_2(self):
         tr = self.socket_transport()
         tr._buffer = [b'data']