simpleperf: add class interface to read elf files.

This is to keep file mapping memory buffer. And support reading
more than one content in one open instance in the future.
It also supports embedded elf files in apks as normal elf files.

Bug: 153039105
Test: run simpleperf_unit_test.
Change-Id: Ia424926d112cbcd9970f11ffa56d047ff6df7872
Merged-In: Ia424926d112cbcd9970f11ffa56d047ff6df7872
(cherry picked from commit 02e2033f9ef34be0189e151bf6fef60b1285afd9)
5 files changed