Test: Add more helper functions for private DNS validation events am: 7656f200 am: 71fe7845

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/2685926



Change-Id: I59f5af2f4debecca42f8e099ab5f8d55195f95c0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>