simpleperf: add callchain in UnwindingResultRecord.

The callchain contains ips and sps returned by unwinder, which may be
useful for debugging.

Bug: 181075274
Test: run simpleperf_unit_test
Test: run simpleperf manually
Change-Id: Ie1a466119fcdc5326471364aff2fb24c22d97bff
4 files changed