startop: Update app_startup_runner to work with iorapd

Script measures app startup times with/without iorapd-based
prefetching against a cold (or warm) baseline.

mlock/fadvise readahead options now use iorapd to exercise
real code to do prefetching.

Bug: 72170747
Change-Id: I28affac3470271e46febb0e22a6dc9543258b4a4