scudo: Split setRandomTag in two. NFCI. am: 706ac40ba7 am: 777be6c3cd

Original change: https://android-review.googlesource.com/c/platform/external/scudo/+/1526378

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Id06d1a842a7cf5daceef7d6ee04dc3967cabcc1b