ART: Clean up arm64 kNumberOfXRegisters usage.

Avoid undefined behavior for arm64 stemming from 1u << 32 in
loops with upper bound kNumberOfXRegisters.

Create iterators for enumerating bits in an integer either
from high to low or from low to high and use them for
<arch>Context::FillCalleeSaves() on all architectures.

Refactor runtime/utils.{h,cc} by moving all bit-fiddling
functions to runtime/base/bit_utils.{h,cc} (together with
the new bit iterators) and all time-related functions to
runtime/base/time_utils.{h,cc}. Improve test coverage and
fix some corner cases for the bit-fiddling functions.

Bug: 13925192
Change-Id: I704884dab15b41ecf7a1c47d397ab1c3fc7ee0f7
diff --git a/runtime/stack.h b/runtime/stack.h
index 5b43848..0db0266 100644
--- a/runtime/stack.h
+++ b/runtime/stack.h
@@ -21,11 +21,11 @@
 #include <string>
 
 #include "arch/instruction_set.h"
+#include "base/bit_utils.h"
 #include "dex_file.h"
 #include "gc_root.h"
 #include "mirror/object_reference.h"
 #include "read_barrier.h"
-#include "utils.h"
 #include "verify_object.h"
 
 namespace art {