qt, refactor: Move InitExecutor class into its own module

This change makes InitExecutor class re-usable by an alternative GUI,
e.g., QML-based one.

src/qt/initexecutor.cpp

@@ -0,0 +1,68 @@
+// Copyright (c) 2014-2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <qt/initexecutor.h>
+
+#include <interfaces/node.h>
+#include <util/system.h>
+#include <util/threadnames.h>
+
+#include <exception>
+
+#include <QDebug>
+#include <QObject>
+#include <QString>
+#include <QThread>
+
+InitExecutor::InitExecutor(interfaces::Node& node) :
+    QObject(), m_node(node)
+{
+    this->moveToThread(&m_thread);
+    m_thread.start();
+}
+
+InitExecutor::~InitExecutor()
+{
+    qDebug() << __func__ << ": Stopping thread";
+    m_thread.quit();
+    m_thread.wait();
+    qDebug() << __func__ << ": Stopped thread";
+}
+
+void InitExecutor::handleRunawayException(const std::exception *e)
+{
+    PrintExceptionContinue(e, "Runaway exception");
+    Q_EMIT runawayException(QString::fromStdString(m_node.getWarnings().translated));
+}
+
+void InitExecutor::initialize()
+{
+    try
+    {
+        util::ThreadRename("qt-init");
+        qDebug() << __func__ << ": Running initialization in thread";
+        interfaces::BlockAndHeaderTipInfo tip_info;
+        bool rv = m_node.appInitMain(&tip_info);
+        Q_EMIT initializeResult(rv, tip_info);
+    } catch (const std::exception& e) {
+        handleRunawayException(&e);
+    } catch (...) {
+        handleRunawayException(nullptr);
+    }
+}
+
+void InitExecutor::shutdown()
+{
+    try
+    {
+        qDebug() << __func__ << ": Running Shutdown in thread";
+        m_node.appShutdown();
+        qDebug() << __func__ << ": Shutdown finished";
+        Q_EMIT shutdownResult();
+    } catch (const std::exception& e) {
+        handleRunawayException(&e);
+    } catch (...) {
+        handleRunawayException(nullptr);
+    }
+}