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

(cherry picked from commit 05752398)

Change-Id: Ia6fb34b137c5e285818d39c3b9794cd4ce6c3219