AirspeedSelector: add synthetic airspeed option

Synthetic airspeed is calculated based on the thrust setpoint
and the thrust<->airpseed model as configured in the parameters.

src/lib/airspeed/airspeed.cpp

@@ -214,3 +214,8 @@ float calc_calibrated_from_true_airspeed(float speed_true, float air_density)
 {
 	return speed_true * sqrtf(air_density / kAirDensitySeaLevelStandardAtmos);
 }
+
+float calc_true_from_calibrated_airspeed(float speed_calibrated, float air_density)
+{
+	return speed_calibrated * sqrtf(kAirDensitySeaLevelStandardAtmos / air_density);
+}

src/lib/airspeed/airspeed.h

@@ -137,6 +137,8 @@ __EXPORT float calc_TAS(float total_pressure, float static_pressure, float tempe
  */
 __EXPORT float calc_calibrated_from_true_airspeed(float speed_true, float air_density);
 
+__EXPORT float calc_true_from_calibrated_airspeed(float speed_calibrated, float air_density);
+
 __END_DECLS
 
 #endif

src/lib/parameters/param_translation.cpp

@@ -142,5 +142,13 @@ param_modify_on_import_ret param_modify_on_import(bson_node_t node)
 		}
 	}
 
+	// 2025-03-19: translate ASPD_FALLBACK_GW to ASPD_FALLBACK
+	{
+		if (strcmp("ASPD_FALLBACK_GW", node->name) == 0) {
+			strcpy(node->name, "ASPD_FALLBACK");
+			PX4_INFO("copying %s -> %s", "ASPD_FALLBACK_GW", "ASPD_FALLBACK");
+		}
+	}
+
 	return param_modify_on_import_ret::PARAM_NOT_MODIFIED;
 }