Merge bitcoin/bitcoin#34820: test: Use asyncio.SelectorEventLoop() over deprecated asyncio.WindowsSelectorEventLoopPolicy(), move loop creation

fa050da980 test: Move event loop creation to network thread (MarcoFalke)
fa9168ffcd test: Use asyncio.SelectorEventLoop() over deprecated asyncio.WindowsSelectorEventLoopPolicy() (MarcoFalke)

Pull request description:

  It is deprecated according to https://docs.python.org/3.14/library/asyncio-policy.html#asyncio.WindowsSelectorEventLoopPolicy The replacement exists since python 3.7

  Also, move the event loop creation to happen in the thread that runs the loop.

ACKs for top commit:
  l0rinc:
    ACK fa050da980
  sedited:
    ACK fa050da980

Tree-SHA512: dce25596a04e8f133630d84c03a770185a81b1bcd0aae975f0dbdd579d22b7b79a9b1172abf46c61d0845d3f5ab4a6414fa0f17c59f0ea0f6fa9bdcac085a2a7

test/functional/test_framework/p2p.py

@@ -740,12 +740,10 @@ class NetworkThread(threading.Thread):
 
         NetworkThread.listeners = {}
         NetworkThread.protos = {}
-        if platform.system() == 'Windows':
-            asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
-        NetworkThread.network_event_loop = asyncio.new_event_loop()
 
     def run(self):
         """Start the network thread."""
+        NetworkThread.network_event_loop = asyncio.SelectorEventLoop() if platform.system() == "Windows" else asyncio.new_event_loop()
         self.network_event_loop.run_forever()
 
     def close(self, *, timeout):

test/functional/test_framework/test_framework.py

@@ -260,7 +260,7 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         self.log.debug('Setting up network thread')
         self.network_thread = NetworkThread()
         self.network_thread.start()
-        self.wait_until(lambda: self.network_thread.network_event_loop.is_running())
+        self.wait_until(lambda: self.network_thread.network_event_loop is not None and self.network_thread.network_event_loop.is_running())
 
         if self.options.usecli:
             if not self.supports_cli: