Add extra systrace for app startup

Added traces for OatFileAssistant, a non trivial amount of time is
spent in DexChecksumUpToDate.

There should be no significant overhead from the tracing since we don't
load oat files very often.

Test: test-art-host
Bug: 132971994
Change-Id: I2cd63f17e948a27174b27148d5dd5b9310bdf457
2 files changed