* sensors: add per-receiver GPS delay parameters
Add SENS_GPS{0,1}_DELAY params to vehicle_gps_position, following the
same device-ID matching pattern used for antenna offsets. Each receiver
can now have its own measurement delay relative to the IMU.
The delay is applied to timestamp_sample before blending. When PPS time
correction is active it takes priority over the parameter-based delay.
When a GPS driver already provides its own timestamp_sample the
per-receiver delay is not applied on top of it.
* fix(ekf2): remove EKF2_GPS_DELAY and perform param transation
* fix(param_translation): fix GPS param migration return values
Add missing return for EKF2_GPS_POS_Z and remove incorrect return for
EKF2_GPS_DELAY (1-to-many migration should not return PARAM_MODIFIED).
* fix(sensors,ekf2): rename pps_compensation and clarify delay default
* fix(ekf2): account for SENS_GPS*_DELAY in observation buffer sizing
* fix(docs): migrate EKF2_GPS_DELAY param
Jacob Dahl