Use image oat file instead of image header for immune spaces

The old immune spaces logic used the oat file information in the
image header instead of the actual oat file pointer. This was
incorrect for the app image case since the app image oat file is
not necessarily at the address specified in the header. This bug
could cause an incorrect immune region that caused large objects
to get freed if they were within this immune region.

Added test.

Bug: 22858531
Change-Id: I243253e61ea1afd42c3bb2414c02ce6dd36d0f9c