Implement Percentage support for gap styles (#1643)

Summary:
X-link: https://github.com/facebook/react-native/pull/44067

X-link: https://github.com/facebook/litho/pull/980

Pull Request resolved: https://github.com/facebook/yoga/pull/1643

Changelog [Internal]:
- Added percentage value for flex layout gap
- Wired up to pass proper available width and height to implement this feature

Reviewed By: NickGerleman

Differential Revision: D56002340

fbshipit-source-id: c0bc86ac70a1391f115c87da99c2ef411535f68b

java/com/facebook/yoga/YogaNode.java

@@ -192,6 +192,8 @@ public abstract class YogaNode implements YogaProps {
 
   public abstract void setGap(YogaGutter gutter, float gapLength);
 
+  public abstract void setGapPercent(YogaGutter gutter, float gapLength);
+
   public abstract float getLayoutX();
 
   public abstract float getLayoutY();