simpleperf: improve generating test files.

To extend the use of generating test files in debug-unwind cmd:
1. Support multiple times in --sample-time option.
2. Keep build ids in test files.
3. Remove the requirement that input files should be recorded with
--keep-failed-unwinding-debug-info.

Bug: none
Test: run simpleperf_unit_test.
Change-Id: I4a9bb4d978733dd6d761e28d5d0de42cb572d57c
2 files changed