Kernel: Move all tasks-related code to the Tasks subdirectory

Author: https://github.com/supercomputer7
Commit: 1b04726c85
Pull-request: https://github.com/SerenityOS/serenity/pull/17604
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/kleinesfilmroellchen ✅

Kernel/SanCov.cpp

@@ -5,7 +5,7 @@
  */
 
 #include <Kernel/Devices/KCOVDevice.h>
-#include <Kernel/Thread.h>
+#include <Kernel/Tasks/Thread.h>
 
 extern bool g_in_early_boot;