alarm_pool_create_with_unused_hardware_alarm() function

Create an alarm pool, claiming an used timer_alarm to back it. The alarm pool will call callbacks from an alarm IRQ Handler on the core of this function is called from. In many situations there is never any need for anything other than the default alarm pool, however you might want to create another if you want alarm callbacks on core 1 or require alarm pools of different priority (IRQ priority based preemption of callbacks)