Merge bitcoin/bitcoin#22987: qa: Fix "RuntimeError: Event loop is closed" on Windows

357f0c7233 ci: Enable more functional tests on Windows MSVC task (Hennadii Stepanov)
f55932678f qa: Fix "RuntimeError: Event loop is closed" on Windows (Hennadii Stepanov)

Pull request description:

  On master (2161a05855), running functional tests that use the P2P interface ends with an error:
  ```
  RuntimeError: Event loop is closed
  ```

  This PR fixes this bug, and enables more functional tests on Windows MSVC CI task.

  More details about bugfix:
  - [What’s New In Python 3.7](https://docs.python.org/3/whatsnew/3.7.html#asyncio)
  - https://bugs.python.org/issue33792
  - actual [change](https://docs.python.org/3.8/library/asyncio-policy.html#asyncio.WindowsSelectorEventLoopPolicy) done in Python 3.8

  Excluded tests, that are listed in the `EXCLUDE_TESTS` environment variable, need more thorough investigation to be enabled.

ACKs for top commit:
  MarcoFalke:
    review ACK 357f0c7233 🌆

Tree-SHA512: d0ba85be81d55c934959ce7402a9c726598125e9751a1de179d16759d0e8b8a915de879c3a62c12d3564c5e0d9649ebd86963744449626efaa42d9eaa99ad3d0

test/functional/test_framework/p2p.py

@@ -577,6 +577,8 @@ class NetworkThread(threading.Thread):
 
         NetworkThread.listeners = {}
         NetworkThread.protos = {}
+        if sys.platform == 'win32':
+            asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())
         NetworkThread.network_event_loop = asyncio.new_event_loop()
 
     def run(self):