add oneshot mode capability

change fmu to task

increase fmu_servo task priority to max and enable true oneshot

use lowest FMU priority which minimizes jitter

constrain oneshot updates to control group 0 events

src/modules/px4iofirmware/registers.c

@@ -325,6 +325,10 @@ registers_set(uint8_t page, uint8_t offset, const uint16_t *values, unsigned num
 		system_state.fmu_data_received_time = hrt_absolute_time();
 		r_status_flags |= PX4IO_P_STATUS_FLAGS_RAW_PWM;
 
+		if (up_pwm_get_oneshot_mode()) {
+			up_pwm_force_update();
+		}
+
 		break;
 
 	/* handle setup for servo failsafe values */