Move from libbacktrace libunwindstack.

libbacktrace is deprecated, so use the new unwindstack object
that replaces this.

Bug: 120606663

Tag: #refactor

Test: Manual - Ran bluetooth_stack_with_facade sent SIGSEGV and
Test: observed valid backtrace (on host and device).
Test: Ran root-canal on host and sent SIGSEGV and observed valid
Test: backtrace (host only executable).
Change-Id: I5c95627b3f674495e0d9d022d2efff1da5ccefc