sceKernelAddTimerEvent implementation (#2906)

* implementation

* add backend (WIP)

* now should be good
- fix implementation based on homebrew tests
- demote log to debug
- make squidbus happy (hopefully)

* fix moved m_name

* fix clang

* replace existing event when its same id and filter

* run timercallback after addEvent and remove useless code

* move KernelSignalRequest to the end

* clang (i hate you)

src/core/libraries/kernel/equeue.h

@@ -152,6 +152,8 @@ public:
 
     int WaitForSmallTimer(SceKernelEvent* ev, int num, u32 micros);
 
+    bool EventExists(u64 id, s16 filter);
+
 private:
     std::string m_name;
     std::mutex m_mutex;