Move scheduler/threadGroup into common-init instead of per-app

This resolves #12229 which pointed out a shutdown deadlock due to
scheduler/checkqueue having been shut down while network message
processing is still running.

src/init.h

@@ -19,7 +19,7 @@ class thread_group;
 void StartShutdown();
 bool ShutdownRequested();
 /** Interrupt threads */
-void Interrupt(boost::thread_group& threadGroup);
+void Interrupt();
 void Shutdown();
 //!Initialize the logging infrastructure
 void InitLogging();
@@ -54,7 +54,7 @@ bool AppInitLockDataDirectory();
  * @note This should only be done after daemonization. Call Shutdown() if this function fails.
  * @pre Parameters should be parsed and config file should be read, AppInitLockDataDirectory should have been called.
  */
-bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler);
+bool AppInitMain();
 
 /** The help message mode determines what help message to show */
 enum HelpMessageMode {