scripts: fix "cannot schedule new futures after interpreter shutdown"

- looks like around python3.9, they changed it so that
  if we don't block on the main thread, it starts to shut things down
- polling thread.join() makes Ctrl+C work. kind of.

```
$ ./electrum/scripts/txradar.py 6bde84a981e72573666fcc51c81ec3f8f4a813709bf16451dce3f106a114d392
Exception in run: RuntimeError('cannot schedule new futures after interpreter shutdown')
Traceback (most recent call last):
  File "/home/user/wspace/electrum/electrum/util.py", line 1218, in wrapper
    return await func(*args, **kwargs)
  File "/home/user/wspace/electrum/electrum/interface.py", line 649, in wrapper_func
    return await func(self, *args, **kwargs)
  File "/home/user/wspace/electrum/electrum/interface.py", line 675, in run
    await self.open_session(ssl_context=ssl_context)
  File "/home/user/wspace/electrum/electrum/interface.py", line 872, in open_session
    async with _RSClient(
  File "/home/user/.local/lib/python3.10/site-packages/aiorpcx/rawsocket.py", line 167, in __aenter__
    _transport, protocol = await self.create_connection()
  File "/home/user/wspace/electrum/electrum/interface.py", line 285, in create_connection
    return await super().create_connection()
  File "/home/user/.local/lib/python3.10/site-packages/aiorpcx/rawsocket.py", line 163, in create_connection
    return await connector.create_connection(
  File "/usr/lib/python3.10/asyncio/base_events.py", line 1036, in create_connection
    infos = await self._ensure_resolved(
  File "/usr/lib/python3.10/asyncio/base_events.py", line 1418, in _ensure_resolved
    return await loop.getaddrinfo(host, port, family=family, type=type,
  File "/usr/lib/python3.10/asyncio/base_events.py", line 863, in getaddrinfo
    return await self.run_in_executor(
  File "/usr/lib/python3.10/asyncio/base_events.py", line 821, in run_in_executor
    executor.submit(func, *args), loop=self)
  File "/usr/lib/python3.10/concurrent/futures/thread.py", line 169, in submit
    raise RuntimeError('cannot schedule new futures after '
RuntimeError: cannot schedule new futures after interpreter shutdown
```

electrum/scripts/bip39_recovery.py

@@ -38,3 +38,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/block_headers.py

@@ -36,3 +36,5 @@ async def f():
 
 # 2. send the subscription
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/estimate_fee.py

@@ -28,3 +28,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/get_history.py

@@ -31,3 +31,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/ln_features.py

@@ -8,6 +8,9 @@ https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md
 import asyncio
 import os
 import time
+from typing import Optional
+
+from aiorpcx import NetAddress
 
 from electrum.logging import get_logger, configure_logging
 from electrum.simple_config import SimpleConfig
@@ -52,7 +55,6 @@ if not os.path.exists(wallet_path):
 
 # open wallet
 wallet = daemon.load_wallet(wallet_path, password=None, upgrade=True)
-wallet.start_network(network)
 
 
 async def worker(work_queue: asyncio.Queue, results_queue: asyncio.Queue, flag):
@@ -67,19 +69,15 @@ async def worker(work_queue: asyncio.Queue, results_queue: asyncio.Queue, flag):
         work = await work_queue.get()
 
         # only check non-onion addresses
-        addr = None
+        addr = None  # type: Optional[NetAddress]
-        for a in work['addrs']:
+        for a in work['addrs']:  # type: NetAddress
-            if "onion" not in a[0]:
+            if not str(a.host).endswith(".onion"):
                 addr = a
         if not addr:
             await results_queue.put(None)
             continue
 
-        # handle ipv4/ipv6
+        connect_str = f"{work['pk'].hex()}@{addr}"
-        if ':' in addr[0]:
-            connect_str = f"{work['pk'].hex()}@[{addr.host}]:{addr.port}"
-        else:
-            connect_str = f"{work['pk'].hex()}@{addr.host}:{addr.port}"
 
         print(f"worker connecting to {connect_str}")
         try:
@@ -177,3 +175,5 @@ async def node_flag_stats(opt_flag: LnFeatures, presync: False):
 
 asyncio.run_coroutine_threadsafe(
     node_flag_stats(FLAG, presync=PRESYNC), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/peers.py

@@ -27,3 +27,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/servers.py

@@ -25,3 +25,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/txbroadcast.py

@@ -34,3 +34,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/txradar.py

@@ -36,3 +36,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/update_default_servers.py

@@ -61,3 +61,5 @@ async def f():
         stopping_fut.set_result(1)
 
 asyncio.run_coroutine_threadsafe(f(), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)

electrum/scripts/watch_address.py

@@ -18,7 +18,7 @@ except Exception:
 config = SimpleConfig()
 
 # start network
-loop = create_and_start_event_loop()[0]
+loop, stopping_fut, loop_thread = create_and_start_event_loop()
 network = Network(config)
 network.start()
 
@@ -45,3 +45,5 @@ class Notifier(SynchronizerBase):
 
 notifier = Notifier(network)
 asyncio.run_coroutine_threadsafe(notifier.watch_queue.put(addr), loop)
+while loop_thread.is_alive():
+    loop_thread.join(1)