[core] Replace std::function with lightweight Callback in CallbackManager (#14853)

esphome/components/modbus_controller/modbus_controller.cpp

@@ -837,17 +837,5 @@ int64_t payload_to_number(const std::vector<uint8_t> &data, SensorValueType sens
   return value;
 }
 
-void ModbusController::add_on_command_sent_callback(std::function<void(int, int)> &&callback) {
-  this->command_sent_callback_.add(std::move(callback));
-}
-
-void ModbusController::add_on_online_callback(std::function<void(int, int)> &&callback) {
-  this->online_callback_.add(std::move(callback));
-}
-
-void ModbusController::add_on_offline_callback(std::function<void(int, int)> &&callback) {
-  this->offline_callback_.add(std::move(callback));
-}
-
 }  // namespace modbus_controller
 }  // namespace esphome