ART: Move read barrier config out of globals

Reduce the global dependencies by refactoring where the read
barrier constants are defined.

Rename read_barier_c.h to read_barier_config.h and ifdef the
C++ parts to have a common header for both C/asm and C++.

Put heap poisoning configuration into its own minimal header.

Fix up transitive includes.

Test: m
Change-Id: I159669ec61e3d1c4c7ddcd79e63b023a0519717a
diff --git a/runtime/thread.h b/runtime/thread.h
index ad4506e..94c0af2 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -40,6 +40,7 @@
 #include "jvalue.h"
 #include "managed_stack.h"
 #include "offsets.h"
+#include "read_barrier_config.h"
 #include "runtime_stats.h"
 #include "suspend_reason.h"
 #include "thread_state.h"