simpleperf: Support trace-offcpu modes for report-sample profiles

`simpleperf report-sample` converts perf.data into a profile in
cmd_report_sample.proto format. This CL supports reading the proto
file with different trace offcpu modes in scripts. It uses the same
logic as report_lib_interface.cpp in aosp/1896057.

Bug: 325484390
Test: run test.py -p TestProtoFileReportLib*
Change-Id: I6374fd62890c882cd3b09e6446b1b9f01bff2e4f
2 files changed