Kernel: Don't log profile data before/after the process/thread lifetime

There were a few cases where we could end up logging profiling events
before or after the associated process or thread exists in the profile:

After enabling profiling we might end up with CPU samples before we
had a chance to synthesize process/thread creation events.

After a thread exits we would still log associated kmalloc/kfree
events. Instead we now just ignore those events.

Kernel/Syscalls/exit.cpp

@@ -19,6 +19,7 @@ void Process::sys$exit(int status)
     }
 
     auto* current_thread = Thread::current();
+    current_thread->set_profiling_suppressed();
     PerformanceManager::add_thread_exit_event(*current_thread);
 
     die();