sensors: move gyro filtering to sensors/vehicle_angular_velocity

- gyro filtering (low-pass and notch) only performed on primary gyro in `sensors/vehicle_angular_velocity` instead of every gyro in `PX4Gyroscope`
 - sample rate is calculated from actual updates (the fixed value was slightly wrong in many cases, and very wrong in a few)
 - In the FIFO case the array is now averaged and published in `sensor_gyro` for filtering downstream. I'll update this in the future to use the full FIFO array (if available), but right now it should be fine.

src/lib/mathlib/math/filter/LowPassFilter2pArray.hpp

@@ -38,6 +38,8 @@
 
 #include "LowPassFilter2p.hpp"
 
+#include <px4_platform_common/defines.h>
+
 namespace math
 {