I'm struggling to understand the difference between nrf_pwr_mgmt_run() and sd_app_evt_wait(). When should I use each one? It looks like nrf_pwr_mgmt_run() calls sd_app_evt_wait() so is it safe to just always use nrf_pwr_mgmt_run()? Is there a reason I would want to bypass nrf_pwr_mgmt_run() and call sd_app_evt_wait() directly?