sdlog2 replay:

- added PRIO_BOOST parameter to avoid log data loss
- added replay mode which disabled logging of uneeded topics
- run mainloop based on polling of either sensor_combined or replay topic
depending on mode
- log ekf2_replay topic

src/modules/sdlog2/params.c

@@ -91,3 +91,15 @@ PARAM_DEFINE_INT32(SDLOG_GPSTIME, 1);
  */
 PARAM_DEFINE_INT32(SDLOG_UTC_OFFSET, 0);
 
+/**
+ * Give logging app higher thread priority to avoid data loss.
+ * This is used for gathering replay logs for the ekf2 module.
+ *
+ * A value of 0 indicates that the default priority is used.
+ * Increasing the parameter in steps of one increases the priority.
+ *
+ * @min 0
+ * @max  3
+ * @group SD Logging
+ */
+PARAM_DEFINE_INT32(SDLOG_PRIO_BOOST, 0);