Use per character suffix for multi image

Use per character suffix for multi image

E.g. if you pull the oat files from the device, you get oat files
with the following names:
system@framework@boot.art

But the name stored in the image header is:
boot.art

So we need to append system@framework@ as a file name prefix to each
image file to get the actual one.

Required for adding oatdump support for app images.

Bug: 22858531
Bug: 27408512

Change-Id: I93dd3f16652400f232e6175670fcd572395879e0