ekf2: baro bias publish minor cleanup

- naming consistency (estimator prefix as "namespace")
 - only publish if baro is available and bias is changing as a small logging optimization
 - avoid unnecessary copying (get const reference to status directly)
 - trivial code style fixes

msg/tools/uorb_rtps_message_ids.yaml

@@ -343,7 +343,7 @@ rtps:
     id: 159
   - msg: event
     id: 160
-  - msg: baro_bias_estimate
+  - msg: estimator_baro_bias
     id: 161
   - msg: internal_combustion_engine_status
     id: 162