Use libunwindstack instead of libbacktrace. am: f44070ed04 am: 97b180383b

Original change: https://android-review.googlesource.com/c/platform/art/+/2045667

Change-Id: I5341b7599c57854db0090251b84386d9c2e802b0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>