Log IMU data at higher rates

[clydemcqueen]

Several options:

• The RISI table contains IMU info, and is logged at 200Hz (the EKF loop rate) if LOG_REPLAY is on
• ArduPilot will publish ROS2 Imu messages at ~120Hz
• There may be a way to get fast IMU messages w/o LOG_REPLAY, look at INS_FAST_SAMPLE: https://ardupilot.org/copter/docs/parameters.html#ins-fast-sample

[clydemcqueen]

A better way is probably to implement fast (loop rate) IMU logging in ArduSub. This is already done in ArduCopter, and it is turned on if you set bit 18 in LOG_BITMASK.

[clydemcqueen]

ArduPilot/ardupilot#28747