simpleperf: check content in build_id_list.

The content in build_id_list may not match files exist in symfs dir,
(like due to interrupted tests).
So in simpleperf binary, do build id check for files in build_id_list.
Also check if files exist in NativeLibDownloader.

Bug: 134164477
Test: run simpleperf_unit_test.
Test: run test.py TestNativeLibDownloader*
Change-Id: Ida435d17d4fead2ba3a14c7766ecaf7cf12448b2
7 files changed