Add immune spaces abstraction

ImmuneSpaces is a set of spaces which are not reclaimable by the GC in
the current collection. This set of spaces does not have requirements
about space adjacency like the old ImmuneRegion. ImmuneSpaces generates
the largest immune region for the GC. Since there is no requirement on
adjacency, it is possible to have multiple non-adjacent applicaton
image files.

For image spaces, we also look at the oat code which is normally after
the application image. In this case, we add the code as part of the
immune region. This is required to have both the boot image and the
zygote space be in the same immune region (for performance reasons).

Bug: 22858531

Change-Id: I5103b31c0e39ad63c594f5557fc848a3b288b43e
19 files changed