Merge bitcoin/bitcoin#34857: test: Remove confusing assert_debug_log in wallet_reindex.py

fa30951af5 test: Remove confusing assert_debug_log in wallet_reindex.py (MarcoFalke)

Pull request description:

  The `wallet_reindex.py` test has many issues:

  * It uses a `assert_debug_log` to ensure the reindex happened via `initload thread exit`. However, no other test uses this pattern, because `restart_node` already achieves the same internally (via `getmempoolinfo.loaded`).
  * The `assert_debug_log` may intermittently fail, because the `initload thread exit` log may happen at any time after the inner thread function (lambda) is fully done.
  * The test uses an `node.syncwithvalidationinterfacequeue()` without any explanation. No other test uses this pattern, because all wallet RPCs, in particular the next one (`gettransaction`) call it internally (via `BlockUntilSyncedToCurrentChain`).

  Fix all issues by removing all confusing, useless, and brittle calls.

  Example failure: https://github.com/bitcoin/bitcoin/actions/runs/22671604602/job/65716917459?pr=34419#step:11:22339

  ```
  ...
   node0 2026-03-04T13:55:23.784715Z (mocktime: 2026-03-04T22:15:17Z) [scheduler] [validationinterface.cpp:185] [operator()] [validation] UpdatedBlockTip: new block hash=24b5cc4c1352bc8841ecbe67a43827acd1adc609bd26b2691e80e89b97eff135 fork block hash=24a4dc8be9c157ac31913397d8bb1653900e12b55539c234039559fdeb6dd2fb (in IBD=true)
   node0 2026-03-04T13:55:23.784851Z (mocktime: 2026-03-04T22:15:17Z) [initload] [util/thread.cpp:22] [TraceThread] initload thread exit
   test  2026-03-04T13:55:23.813824Z TestFramework (ERROR): Unexpected exception:
                                     Traceback (most recent call last):
                                       File "/home/admin/actions-runner/_work/_temp/test/functional/test_framework/test_framework.py", line 142, in main
                                         self.run_test()
                                       File "/home/admin/actions-runner/_work/_temp/build/test/functional/wallet_reindex.py", line 90, in run_test
                                         self.birthtime_test(node, miner_wallet)
                                       File "/home/admin/actions-runner/_work/_temp/build/test/functional/wallet_reindex.py", line 64, in birthtime_test
                                         with node.assert_debug_log(expected_msgs=["initload thread exit"]):
                                       File "/usr/lib/python3.12/contextlib.py", line 144, in __exit__
                                         next(self.gen)
                                       File "/home/admin/actions-runner/_work/_temp/test/functional/test_framework/test_node.py", line 607, in assert_debug_log
                                         self._raise_assertion_error(f'Expected message(s) {remaining_expected!s} '
                                       File "/home/admin/actions-runner/_work/_temp/test/functional/test_framework/test_node.py", line 241, in _raise_assertion_error
                                         raise AssertionError(self._node_msg(msg))
                                     AssertionError: [node 0] Expected message(s) ['initload thread exit'] not found in log:
  ```

  Diff to reproduce failure:

  ```diff
  diff --git a/src/util/thread.cpp b/src/util/thread.cpp
  index 0fde73c4e2..de4c05e752 100644
  --- a/src/util/thread.cpp
  +++ b/src/util/thread.cpp
  @@ -8,2 +8,3 @@
   #include <util/log.h>
  +#include <util/time.h>
   #include <util/threadnames.h>
  @@ -21,2 +22,3 @@ void util::TraceThread(std::string_view thread_name, std::function<void()> threa
           thread_func();
  +    UninterruptibleSleep(999ms);
           LogInfo("%s thread exit", thread_name);
  diff --git a/test/functional/wallet_reindex.py b/test/functional/wallet_reindex.py
  index 71ab69e01b..649df4301a 100755
  --- a/test/functional/wallet_reindex.py
  +++ b/test/functional/wallet_reindex.py
  @@ -62,2 +62,3 @@ class WalletReindexTest(BitcoinTestFramework):

  +        import time; time.sleep(1) # Wait for previous initload thread to exit fully
           # Reindex and wait for it to finish
  ```

  Before on master: Test fails
  After on this pull: Test passes

ACKs for top commit:
  rkrux:
    ACK fa30951af5 if this PR needs to be backported.

Tree-SHA512: 1e6599511e09b5b9ac4aed96a6b1b8239d5dc63b164fc0c163b6f9f5bc72c1c61f72ad8256a01875208d825af46d057c4d9de61758002f256388ddb324006bb5

test/functional/wallet_reindex.py

@@ -60,10 +60,8 @@ class WalletReindexTest(BitcoinTestFramework):
         assert_equal(wallet_watch_only.gettransaction(tx_id)['confirmations'], 50)
         assert_equal(wallet_watch_only.getbalances()['mine']['trusted'], 2)
 
-        # Reindex and wait for it to finish
-        with node.assert_debug_log(expected_msgs=["initload thread exit"]):
-            self.restart_node(0, extra_args=['-reindex=1', f'-mocktime={self.node_time}'])
-        node.syncwithvalidationinterfacequeue()
+        self.log.info("Reindex ...")  # restart_node waits for it to finish
+        self.restart_node(0, extra_args=[ f'-mocktime={self.node_time}'])
 
         # Verify the transaction is still 'confirmed' after reindex
         wallet_watch_only = node.get_wallet_rpc('watch_only')