simpleperf: unwind samples in files recorded with debug info.

In debug_unwind cmd, support unwinding samples for perf.data generated
with --keep-failed-unwinding-debug-info.

Also fix an error dumping debug unwind files in record cmd.

Bug: 181075274
Test: run simpleperf_unit_test
Change-Id: I628c81b8b9936138be536d52afdfdbebfc80ebd2
4 files changed