- WelfordMeanVector now computes covariance
- use Kahan summation for Welford mean (but continue using float32 for actual mean, etc)
- WelfordMean and WelfordMeanVector handle initial value and count roll over
- Welford mean count rollover at 16 bit max to prevent numerical issues and shift weight to newer samples
- sensors/vehicle_imu: update Welford mean usage (now simplified with resets removed)
- fix vehicle_imu_status accel var, now properly rotated with full covariance matrix
- gyro_calibration: update Welford mean usage
- this was an experiment to casually monitor sensor offsets relative to temperature, but now that all calibration offsets can be adjusted post-flight the stored temperature can be misleading
- deleting to save a little bit of flash (and storing the temperature wasn't useful)
- centralize logic for selecting a preferred calibration slot
- automatically use existing calibration slot if it exists, otherwise
find first available slot, with a preference for a requested index
- existing commander calibration methods rewrite all calibration slots
to match current sensor ordering