lnworker: history to include close tx for channel backups

- scenario:
  - reuse same seed between two devices, LN enabled on both
  - open channel using device1, import chan backup on device2
  - local-force-close channel using device1
  - tx1 (ctx) gets into mempool (or even mined), tx2 (sweep tx for to_local) is a local (future) tx
  - history tab on device1 shows tx1 and tx2
  - history tab on device2 was showing only tx2, and no info about tx1
    - device2 knows about tx1, it was just not showing it previously.
      With this commit, tx1 is now shown in the history.
    - note: tx1 might linger in the mempool for an indeterminate amount of time, or even become local.
      During that time, it is confusing on device2 not to show any feedback. Also,
      if tx1 becomes local, it is useful to be able to rebroadcast it.

electrum/lnworker.py

@@ -14,7 +14,6 @@ from typing import (Optional, Sequence, Tuple, List, Set, Dict, TYPE_CHECKING,
                     NamedTuple, Union, Mapping, Any, Iterable, AsyncGenerator, DefaultDict, Callable, Awaitable)
 import threading
 import socket
-import aiohttp
 import json
 from datetime import datetime, timezone
 from functools import partial, cached_property
@@ -22,7 +21,9 @@ from collections import defaultdict
 import concurrent
 from concurrent import futures
 import urllib.parse
+import itertools
 
+import aiohttp
 import dns.resolver
 import dns.exception
 from aiorpcx import run_in_thread, NetAddress, ignore_after
@@ -1063,7 +1064,7 @@ class LNWallet(LNWorker):
         current_height = self.wallet.adb.get_local_height()
         out = {}
         # add funding events
-        for chan in self.channels.values():
+        for chan in itertools.chain(self.channels.values(), self.channel_backups.values()):  # type: AbstractChannel
             item = chan.get_funding_height()
             if item is None:
                 continue