sensors: move voting into sensors module

- voting is now at a central place instead of duplicated within the
  estimators
  -> this also means that estimators that did not do voting so far,
     now have voting, like ekf2
- estimators requiring more than that can still subscribe to the raw
  sensors
- allows sensors_combined to be 3 times smaller
  - reduces logger, memcpy (cache) & RAM overhead
- all modules requiring only 1 or 2 sensor values now automatically get
  the voted result
- this also adds voting to baro

src/modules/commander/commander.cpp

@@ -1788,7 +1788,7 @@ int commander_thread_main(int argc, char *argv[])
 			 * vertical separation from other airtraffic the operator has to know when the
 			 * barometer is inoperational.
 			 * */
-			if (hrt_elapsed_time(&sensors.baro_timestamp[0]) < FAILSAFE_DEFAULT_TIMEOUT) {
+			if (hrt_elapsed_time(&sensors.baro_timestamp) < FAILSAFE_DEFAULT_TIMEOUT) {
 				/* handle the case where baro was regained */
 				if (status_flags.barometer_failure) {
 					status_flags.barometer_failure = false;