Modify the offline handling interface.

- Add a new function Backtrace::UnwindOffline that takes the stack data.
- Modify BacktraceMap::CreateOffline so it doesn't take the stack data.
  This makes it easier to reuse the map object created this way.

Reusing the map object increases simpleperf speed (unwinds per second) by 50%.

Test: backtrace_test libunwindstack_test
Change-Id: I90cfbae9e50d95d8a0e3cd394b33ba36d65d45f7
5 files changed