simpleperf: add --print-event-count in report cmd.

--print-event-count is used to print event counts associated
with each sample. The event counts can be added by --add-counter
in record cmd.

Bug: 211001574
Test: run simpleperf_unit_test

Change-Id: I93f0760de0a8b10bb9ca4fa3dc4c71c0a2e80624
5 files changed