Merge bitcoin/bitcoin#23005: multiprocess: Delay wallet client construction

ad085f9ba1 multiprocess: Delay wallet client construction (Russell Yanofsky)

Pull request description:

  Delay wallet client construction until after logging, thread and other init for two reasons:

  - More responsive multiprocess GUI startup. When bitcoin-gui is started this moves the call from bitcoin-gui to bitcoin-node that spawns bitcoin-wallet off of the GUI event thread and onto the background GUI init executor thread.

  - Avoids feature_logging.py test failures with bitcoin-node by making bitcoin-wallet logging start after bitcoin-node logging starts,
    because the tests are not written to handle the bitcoin-wallet logging init code running first.

  This partially reverts commit b266b3e0bf, moving wallet client creation back to the place it was located before.

  ---

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10).

ACKs for top commit:
  laanwj:
    code review ACK ad085f9ba1
  hebasto:
    ACK ad085f9ba1, I have reviewed the code and it looks OK.

Tree-SHA512: 74d957ce2ee096db745c517124f60800185814b06c20db676090e10dce1b90311adbab02865a69731f8c39b9365f9ee14be0830ca1368cac9b474801ea92bad5

src/qt/splashscreen.cpp

@@ -194,6 +194,7 @@ void SplashScreen::subscribeToCoreSignals()
     // Connect signals to client
     m_handler_init_message = m_node->handleInitMessage(std::bind(InitMessage, this, std::placeholders::_1));
     m_handler_show_progress = m_node->handleShowProgress(std::bind(ShowProgress, this, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3));
+    m_handler_init_wallet = m_node->handleInitWallet([this]() { handleLoadWallet(); });
 }
 
 void SplashScreen::handleLoadWallet()