Move timer to concurrent/

Tests/TactilityKernel/ThreadTest.cpp

@@ -1,6 +1,6 @@
 #include "doctest.h"
-#include "tactility/delay.h"
 
+#include <tactility/delay.h>
 #include <tactility/concurrent/thread.h>
 
 TEST_CASE("when a thread is started then its callback should be called") {

Tests/TactilityKernel/TimerTest.cpp

@@ -1,9 +1,10 @@
 #include "doctest.h"
 
-#include "tactility/timer.h"
-#include "tactility/delay.h"
 #include <atomic>
 
+#include <tactility/concurrent/timer.h>
+#include <tactility/delay.h>
+
 TEST_CASE("timer_alloc and timer_free should handle allocation and deallocation") {
     auto callback = [](void* context) {};
     struct Timer* timer = timer_alloc(TIMER_TYPE_ONCE, 10, callback, nullptr);