Merge "Backfill atom tests for new event metric format" am: 9706e6072f am: 291820727f am: fbe3035f4c

Original change: https://android-review.googlesource.com/c/platform/external/libtextclassifier/+/1922001

Change-Id: Idc0ebea41ee73fff4911a4e63f66ae83f30e75c5