test_zzz_integration: don't mix threading/multiprocessing

Use a Process instead of a Thread for ircserver, as we are already using
Processes for the clients. This addresses the following 3.12 warning:
  /usr/lib/python3.12/multiprocessing/popen_fork.py:66: DeprecationWarning: This process (pid=1299670) is multi-threaded, use of fork() may lead to deadlocks in the child.
      self.pid = os.fork()

Author: paravoid

tests/test_zzz_integration.py

@@ -7,7 +7,6 @@
 import multiprocessing.synchronize
 import pathlib
 import socket
-import threading
 import time
 from typing import Any
 
@@ -60,8 +59,8 @@ def on_pubmsg(self, _: irc.connection.Factory, __: irc.client.Event) -> None:
 
 
 @pytest.fixture(name="main")
-def fixture_main(tmp_path: pathlib.Path) -> threading.Thread:
-    """Fixture for ircstream main(), running it in a thread."""
+def fixture_main(tmp_path: pathlib.Path) -> multiprocessing.Process:
+    """Fixture for ircstream main(), running it in a Process."""
     # test a semi-stock config, with default ports etc.
     tmp_config = tmp_path / "ircstream-integration.conf"
     tmp_config.write_text(
@@ -84,7 +83,7 @@ def fixture_main(tmp_path: pathlib.Path) -> threading.Thread:
     )
     args = ("--config", str(tmp_config))
 
-    main = threading.Thread(target=ircstream.run, args=(args,), daemon=True)
+    main = multiprocessing.Process(target=ircstream.run, args=(args,), daemon=True)
     main.start()
     time.sleep(0.1)
     if not main.is_alive():