simpleperf: add python report interface on linux.

1. Build libsimpleperf_report.so on host, which exports functions
   to access samples.
2. Add simpleperf_report_lib.py to wrap libsimpleperf_report.so.
3. Write report_sample.py to test simpleperf_report_lib.py. The
   output format of report_sample.py matches the need of building
   FlameGraph.

Bug: http://b/31069528
Test: run report_sample.py on perf.data.
Test: run simpleperf_unit_test.

Change-Id: I4949f8ea506f12101a9c4fb4c896957c96676853
10 files changed