Use yield() where possible

Replaced calls of this_thread::sleep_* with this_thread::yield(), which
yields the thread to the OS' scheduler.

include/TLuaEngine.h

@@ -150,6 +150,7 @@ public:
     void CancelEventTimers(const std::string& EventName, TLuaStateId StateId);
     sol::state_view GetStateForPlugin(const fs::path& PluginPath);
     TLuaStateId GetStateIDForPlugin(const fs::path& PluginPath);
+    void AddResultToCheck(const std::shared_ptr<TLuaResult>& Result);
 
     static constexpr const char* BeamMPFnNotFoundError = "BEAMMP_FN_NOT_FOUND";