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

(cherry picked from commit 4e9c4e746617bad6a012d799d2f5cf9e01d24ea2)

Change-Id: I67a536c33aeed603b252d8e0f75622c9efbf2559
diff --git a/runtime/class_table.cc b/runtime/class_table.cc
index 55ff73d..0600876 100644
--- a/runtime/class_table.cc
+++ b/runtime/class_table.cc
@@ -113,6 +113,10 @@
   classes_.back().Insert(GcRoot<mirror::Class>(klass));
 }
 
+void ClassTable::InsertWithoutLocks(mirror::Class* klass) {
+  classes_.back().Insert(GcRoot<mirror::Class>(klass));
+}
+
 void ClassTable::InsertWithHash(mirror::Class* klass, size_t hash) {
   WriterMutexLock mu(Thread::Current(), lock_);
   classes_.back().InsertWithHash(GcRoot<mirror::Class>(klass), hash);