Merge "Add add3prf.py and call it from get_rust_pky.py" am: bb90c3ad26 am: 5052c70dd8

Original change: https://android-review.googlesource.com/c/platform/development/+/1451282

Change-Id: I3a610eb57ad4dfa80291a8cc1e33a7e339f5834a