This implementation uses a union containing the Array implementing the MultiElement field data and a struct made from element names.
it allow to replace the following sintax:
settings.PitchRatePID[STABILIZATIONSETTINGS_PITCHRATEPID_KP]
with a more concise and less error prone
settings.PitchRatePID.fields.Kp
while allowing the direct array access using the notation
settings.PitchRatePID.data[n]