simpleperf: improve recording unwinding results.

1. Add MAP_MISSING result type.
2. Pass --log option to the simpleperf process running in app's context,
  in order to dump unwinding results when profiling android apps.

Bug: http://b/69383534
Test: run simpleperf_unit_test.
Test: run simpleperf manually.
Change-Id: I72173060a5808e5ffb7318640509cabe53395063
6 files changed