message: init: use std::thread for ThreadImport()
  Mentioned in which removed the boost::interruption_point()
  in ThreadImport().
diff: @@ -147,6 +147,8 @@ NODISCARD static bool CreatePidFile()
  static std::unique_ptr<ECCVerifyHandle> globalVerifyHandle;
  +static std::thread g_load_block;
  +
  static boost::thread_group threadGroup;
  void Interrupt(NodeContext& node)
  @@ -209,8 +211,9 @@ void Shutdown(NodeContext& node)
  StopTorControl();
  // After everything has been shut down, but before things get flushed, stop the
  - // CScheduler/checkqueue threadGroup
  + // CScheduler/checkqueue, threadGroup and load block thread.
  if (node.scheduler) node.scheduler->stop();
  + if (g_load_block.joinable()) g_load_block.join();
  threadGroup.interrupt_all();
  threadGroup.join_all();
  @@ -624,7 +627,6 @@ struct CImportingNow
  static void ThreadImport(ChainstateManager& chainman, std::vector<fs::path> vImportFiles)
  {
  const CChainParams& chainparams = Params();
  - util::ThreadRename("loadblk");
  ScheduleBatchPriority();
  {
  @@ -1675,7 +1677,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node)
  vImportFiles.push_back(strFile);
  }
  - threadGroup.create_thread([=, &chainman] { ThreadImport(chainman, vImportFiles); });
  + g_load_block = std::thread(&TraceThread<std::function<void()>>, "loadblk", [=, &chainman]{ ThreadImport(chainman, vImportFiles); });
  // Wait for genesis block to be processed
  {
  