change gyro & accel dt from float to uint64. This has the benefit of

msg/ekf2_replay.msg

msg/sensor_combined.msg

...ples/ekf_att_pos_estimator/ekf_att_pos_estimator_main.cpp

src/modules/ekf2/ekf2_main.cpp

src/modules/sdlog2/sdlog2_messages.h

src/modules/sensors/voted_sensors_update.cpp