Kernel: Use a separate timer for profiling the system

This updates the profiling subsystem to use a separate timer to
trigger CPU sampling. This timer has a higher resolution (1000Hz)
and is independent from the scheduler. At a later time the
resolution could even be made configurable with an argument for
sys$profiling_enable() - but not today.

Kernel/Scheduler.cpp

@@ -10,7 +10,6 @@
 #include <AK/Time.h>
 #include <Kernel/Debug.h>
 #include <Kernel/Panic.h>
-#include <Kernel/PerformanceManager.h>
 #include <Kernel/Process.h>
 #include <Kernel/RTC.h>
 #include <Kernel/Scheduler.h>
@@ -501,8 +500,6 @@ void Scheduler::timer_tick(const RegisterState& regs)
         return; // TODO: This prevents scheduling on other CPUs!
 #endif
 
-    PerformanceManager::add_cpu_sample_event(*current_thread, regs);
-
     if (current_thread->tick())
         return;