Merge #17070: wallet: Avoid showing GUI popups on RPC errors

facec1c643 wallet: Avoid showing GUI popups on RPC errors (MarcoFalke)

Pull request description:

  RPC errors and warnings are shown as popups in the GUI instead of being returned to the RPC caller. For example,

  ```
  $ ./src/bitcoin-cli loadwallet $(pwd)/./test/functional/data/wallets/high_minversion/
  error code: -4
  error message:
  Wallet loading failed.
  ```

  gives me a GUI popup and no reason why loading the wallet failed.

  After this pull request:

  ```
  $ ./src/bitcoin-cli loadwallet $(pwd)/./test/functional/data/wallets/high_minversion/
  error code: -4
  error message:
  Wallet loading failed: Error loading /home/marco/workspace/btc_bitcoin_core/./test/functional/data/wallets/high_minversion/wallet.dat: Wallet requires newer version of Bitcoin Core

ACKs for top commit:
  laanwj:
    Code review ACK facec1c643

Tree-SHA512: c8274bbb02cfcf71676eeec1e773e51fb3538cf93f82e7cb8536f4716d44ed819cdc162dfc039ac7386a4db381a734cdb27fd32567043a1180c02519fbcba194

src/qt/walletcontroller.cpp

@@ -12,6 +12,7 @@
 
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
+#include <util/string.h>
 
 #include <algorithm>
 
@@ -226,7 +227,7 @@ void CreateWalletActivity::finish()
     if (!m_error_message.empty()) {
         QMessageBox::critical(m_parent_widget, tr("Create wallet failed"), QString::fromStdString(m_error_message));
     } else if (!m_warning_message.empty()) {
-        QMessageBox::warning(m_parent_widget, tr("Create wallet warning"), QString::fromStdString(m_warning_message));
+        QMessageBox::warning(m_parent_widget, tr("Create wallet warning"), QString::fromStdString(Join(m_warning_message, "\n")));
     }
 
     if (m_wallet_model) Q_EMIT created(m_wallet_model);
@@ -267,7 +268,7 @@ void OpenWalletActivity::finish()
     if (!m_error_message.empty()) {
         QMessageBox::critical(m_parent_widget, tr("Open wallet failed"), QString::fromStdString(m_error_message));
     } else if (!m_warning_message.empty()) {
-        QMessageBox::warning(m_parent_widget, tr("Open wallet warning"), QString::fromStdString(m_warning_message));
+        QMessageBox::warning(m_parent_widget, tr("Open wallet warning"), QString::fromStdString(Join(m_warning_message, "\n")));
     }
 
     if (m_wallet_model) Q_EMIT opened(m_wallet_model);

src/qt/walletcontroller.h

@@ -100,7 +100,7 @@ protected:
     QProgressDialog* m_progress_dialog{nullptr};
     WalletModel* m_wallet_model{nullptr};
     std::string m_error_message;
-    std::string m_warning_message;
+    std::vector<std::string> m_warning_message;
 };