ekf2 replay: add statistics output when replay finished

The error counter is an indicator that the logger missed samples or dropped
due to a too small write buffer.

src/modules/replay/replay.hpp

@@ -97,6 +97,10 @@ protected:
 
 		std::streampos next_read_pos;
 		uint64_t next_timestamp; ///< timestamp of the file
+
+		// statistics
+		int error_counter = 0;
+		int publication_counter = 0;
 	};
 
 	/**