Revert^2 "Hash-based DexCache field array."

Test: testrunner.py --host --interpreter
Bug: 30627598

This reverts commit 6374c58f2ea403b3a05fb27376110fe4d0fc8e3f.

Change-Id: I275508e288a85d3aa08f7405a1a4f362af43b775
diff --git a/runtime/linear_alloc.h b/runtime/linear_alloc.h
index df7f17d..384b2e3 100644
--- a/runtime/linear_alloc.h
+++ b/runtime/linear_alloc.h
@@ -29,6 +29,7 @@
   explicit LinearAlloc(ArenaPool* pool);
 
   void* Alloc(Thread* self, size_t size) REQUIRES(!lock_);
+  void* AllocAlign16(Thread* self, size_t size) REQUIRES(!lock_);
 
   // Realloc never frees the input pointer, it is the caller's job to do this if necessary.
   void* Realloc(Thread* self, void* ptr, size_t old_size, size_t new_size) REQUIRES(!lock_);