Call madvise hints for image dex files

After opening image spaces, perform madvise hints for the
corresponding dex files.

Moved kMadviseDexFileAccesses to oat_file.cc to not have this enabled
yet.

Bug: 63178181
Test: make and flash

Change-Id: I60f918274251629cd0e829f0862d9a2528216c08
3 files changed