gptimer_new_timer() function

- ESP_OK: Create GPTimer successfully - ESP_ERR_INVALID_ARG: Create GPTimer failed because of invalid argument - ESP_ERR_NO_MEM: Create GPTimer failed because out of memory - ESP_ERR_NOT_FOUND: Create GPTimer failed because all hardware timers are used up and no more free one - ESP_FAIL: Create GPTimer failed because of other error

The newly created timer is put in the "init" state.