Kernel: Add a syscall to clear the profiling buffer

While profiling all processes the profile buffer lives forever.
Once you have copied the profile to disk, there's no need to keep it
in memory. This syscall surfaces the ability to clear that buffer.

Kernel/Process.cpp

@@ -700,6 +700,12 @@ bool Process::create_perf_events_buffer_if_needed()
     return !!m_perf_event_buffer;
 }
 
+void Process::delete_perf_events_buffer()
+{
+    if (m_perf_event_buffer)
+        m_perf_event_buffer = nullptr;
+}
+
 bool Process::remove_thread(Thread& thread)
 {
     ProtectedDataMutationScope scope { *this };