Remove enum count macros

Summary:
@public
Removes all `YG...Count` macros for enums and replaces them with `facebook::yoga::enums::count<YG...>()`.
This removes the need to manually maintain enum counts.

Same as D13597449, working around a defect in clang < 3.9

Reviewed By: amir-shalem

Differential Revision: D13634622

fbshipit-source-id: 344dc70e167b0caf746fe396cedd200f54e52219

yoga/YGStyle.h

@@ -9,6 +9,7 @@
 #include <array>
 #include <initializer_list>
 #include "CompactValue.h"
+#include "YGEnums.h"
 #include "YGFloatOptional.h"
 #include "Yoga-internal.h"
 #include "Yoga.h"
@@ -29,7 +30,8 @@ private:
 
 public:
   using Dimensions = facebook::yoga::detail::Values<2>;
-  using Edges = facebook::yoga::detail::Values<YGEdgeCount>;
+  using Edges =
+      facebook::yoga::detail::Values<facebook::yoga::enums::count<YGEdge>()>;
 
   /* Some platforms don't support enum bitfields,
      so please use BITFIELD_ENUM_SIZED(BITS_COUNT) */