Remove libprocinfo, libbacktrace, libunwindstack

These projects have moved to a different location.
platform/system/core [libprocinfo] -> platform/system/libprocinfo
platform/system/core [libbacktrace] -> platform/system/unwinding [libbacktrace]
platform/system/core [libunwindstack] -> platform/system/unwinding [libunwindstack]

BUG: 163786882
Test: Local build + TH
Change-Id: Id6d278d917236df0ffd40b5c32593856e112cb5b
413 files changed