Move the receiver inter-frame measurements down into the protocol layer
Adds accuracy to the frame rate measurements used to configure RC smoothing. Prevents looptime delays and jitter from affecting the calculations. Significantly improves the accuracy of the measurement in cases where CPU load is high.
Implemented so that each protocol can individually provide the functionality if appropriate. If a protocol doesn't support the more granular measurement then the system will fallback to the original measurement calculated in the RX task.