Kernel: Implement software context switching and Processor structure

Moving certain globals into a new Processor structure for
each CPU allows us to eventually run an instance of the
scheduler on each CPU.

Kernel/Tasks/SyncTask.cpp

@@ -35,6 +35,7 @@ void SyncTask::spawn()
 {
     Thread* syncd_thread = nullptr;
     Process::create_kernel_process(syncd_thread, "SyncTask", [] {
+        dbg() << "SyncTask is running";
         for (;;) {
             VFS::the().sync();
             Thread::current->sleep(1 * TimeManagement::the().ticks_per_second());