Unify ART's various implementations of bit_cast.

ART had several implementations of art::bit_cast:

1. one in runtime/base/casts.h, declared as:

   template <class Dest, class Source>
   inline Dest bit_cast(const Source& source);

2. another one in runtime/utils.h, declared as:

   template<typename U, typename V>
   static inline V bit_cast(U in);

3. and a third local version, in runtime/memory_region.h,
   similar to the previous one:

   template<typename Source, typename Destination>
   static Destination MemoryRegion::local_bit_cast(Source in);

This CL removes versions 2. and 3. and changes their callers
to use 1. instead.  That version was chosen over the others
as:
- it was the oldest one in the code base; and
- its syntax was closer to the standard C++ cast operators,
  as it supports the following use:

    bit_cast<Destination>(source)

  since `Source' can be deduced from `source'.

Change-Id: I7334fd5d55bf0b8a0c52cb33cfbae6894ff83633
diff --git a/compiler/dex/quick/arm64/fp_arm64.cc b/compiler/dex/quick/arm64/fp_arm64.cc
index a8ec6c0..49b15fe 100644
--- a/compiler/dex/quick/arm64/fp_arm64.cc
+++ b/compiler/dex/quick/arm64/fp_arm64.cc
@@ -449,7 +449,7 @@
 }
 
 bool Arm64Mir2Lir::GenInlinedRound(CallInfo* info, bool is_double) {
-  int32_t encoded_imm = EncodeImmSingle(bit_cast<float, uint32_t>(0.5f));
+  int32_t encoded_imm = EncodeImmSingle(bit_cast<uint32_t, float>(0.5f));
   A64Opcode wide = (is_double) ? WIDE(0) : UNWIDE(0);
   RegLocation rl_src = info->args[0];
   RegLocation rl_dest = (is_double) ? InlineTargetWide(info) : InlineTarget(info);