ART: Some Quick cleanup

Make several fields const in CompilationUnit. May benefit some Mir2Lir
code that repeats tests, and in general immutability is good.

Remove compiler_internals.h and refactor some other headers to reduce
overly broad imports (and thus forced recompiles on changes).

Change-Id: I898405907c68923581373b5981d8a85d2e5d185a
diff --git a/compiler/dex/local_value_numbering.h b/compiler/dex/local_value_numbering.h
index 9b89c95..aef8c6d 100644
--- a/compiler/dex/local_value_numbering.h
+++ b/compiler/dex/local_value_numbering.h
@@ -19,7 +19,7 @@
 
 #include <memory>
 
-#include "compiler_internals.h"
+#include "base/logging.h"
 #include "global_value_numbering.h"
 #include "utils/arena_object.h"
 #include "utils/dex_instruction_utils.h"