Switch storage in YGStyle to CompactValue

Summary:
@public

Switches the storage in `facebook::yoga::detail::Values` from `YGValue` to `facebook::yoga::detail::CompactValue`.
This cuts heap size for arrays of values in half.

Reviewed By: SidharthGuglani

Differential Revision: D13465586

fbshipit-source-id: 49a4d6d29a73bdd44843b1f3c57bf746050c94d6

yoga/CompactValue.h

@@ -6,7 +6,7 @@
  */
 #pragma once
 
-#include <yoga/YGValue.h>
+#include "YGValue.h"
 
 #include <cmath>
 #include <cstdint>
@@ -73,6 +73,10 @@ class CompactValue {
     return std::isnan(value) ? ofUndefined() : of<Unit>(value);
   }
 
+  static constexpr CompactValue ofZero() noexcept {
+    return CompactValue{Payload{ZERO_BITS_POINT}};
+  }
+
   static constexpr CompactValue ofUndefined() noexcept {
     return CompactValue{};
   }