Add rule to convert WIFI_FEATURE_IMU_DETECTION

to the equivalent soong variable.

Bug: 287607876
Test: Manual test - add a log message to wifi_ext that
       only prints if the proper flag is enabled.
       Check whether the log is displayed, both before
       and after this change.
Change-Id: Id9bfc81384384b915e9772a2016a9843a57897db