simpleperf: export meta info in report_sample.proto.

To support perf.data generated with --trace-offcpu option,
update interface in report_sample.proto:
1. Add meta info to show all event types.
2. Add event_type_id in each sample to show which even type it belongs to.

Bug: http://b/37572306
Test: run simpleperf_unit_test.
Change-Id: I2878979ec2023904df1006ce353dcf233b6a2642
6 files changed