Smarter image layout

Smarter image layout

Put strings in the dex file that resolves them.

Depth first traversal with overrides for class and dex cache. The
work list keeps track of what oat_index with each pushed item. This
means the static fields of a class will usually be in the same image.

Added layout test to image_test to make sure things are somewhat
reasonably attributed.

Bug: 28640955

Test: test-art-host

Change-Id: I67a536c33aeed603b252d8e0f75622c9efbf2559