Update thread-roots concurrently during uffd compaction am: cce3151716

Original change: https://android-review.googlesource.com/c/platform/art/+/2390332

Change-Id: I561fe41fb35b9f955f93fb3f6111c8603a5c4f15
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>