Support "align-content: space-evenly" (#1422)

Summary:
X-link: https://github.com/facebook/react-native/pull/41019

### Changes made
- Regenerated tests (as some aspect ratio tests seem to be out of date compared to the fixtures)
- Added SpaceEvenly variant to the "Align" enums (via enums.py)
- Implemented `align-content: space-evenly` alignment in CalculateLayout.cpp
- Added generated tests `align-content: space-evenly`
- Updated NumericBitfield test to account for the fact that the Align enum now requires more bits (this bit could do with being reviewed as I am not 100% certain that it's valid to just update the test like this).

### Changes not made
- Any attempt to improve the spec-compliance of content alignment in general (e.g. I think https://github.com/facebook/yoga/pull/1013 probably still needs to happen)

Pull Request resolved: https://github.com/facebook/yoga/pull/1422

Reviewed By: yungsters

Differential Revision: D50305438

Pulled By: NickGerleman

fbshipit-source-id: ef9f6f14220a0db066bc30db8dd690a4a82a0b00

yoga/YGEnums.cpp

@@ -27,6 +27,8 @@ const char* YGAlignToString(const YGAlign value) {
       return "space-between";
     case YGAlignSpaceAround:
       return "space-around";
+    case YGAlignSpaceEvenly:
+      return "space-evenly";
   }
   return "unknown";
 }

yoga/YGEnums.h

@@ -21,7 +21,8 @@ YG_ENUM_SEQ_DECL(
     YGAlignStretch,
     YGAlignBaseline,
     YGAlignSpaceBetween,
-    YGAlignSpaceAround)
+    YGAlignSpaceAround,
+    YGAlignSpaceEvenly)
 
 YG_ENUM_SEQ_DECL(
     YGDimension,

yoga/algorithm/CalculateLayout.cpp

@@ -2036,6 +2036,18 @@ static void calculateLayoutImpl(
             currentLead += remainingAlignContentDim / 2;
           }
           break;
+        case Align::SpaceEvenly:
+          if (availableInnerCrossDim > totalLineCrossDim) {
+            currentLead +=
+                remainingAlignContentDim / static_cast<float>(lineCount + 1);
+            if (lineCount > 1) {
+              crossDimLead =
+                  remainingAlignContentDim / static_cast<float>(lineCount + 1);
+            }
+          } else {
+            currentLead += remainingAlignContentDim / 2;
+          }
+          break;
         case Align::SpaceBetween:
           if (availableInnerCrossDim > totalLineCrossDim && lineCount > 1) {
             crossDimLead =
@@ -2192,6 +2204,7 @@ static void calculateLayoutImpl(
               case Align::Auto:
               case Align::SpaceBetween:
               case Align::SpaceAround:
+              case Align::SpaceEvenly:
                 break;
             }
           }

yoga/enums/Align.h

@@ -24,16 +24,17 @@ enum class Align : uint8_t {
   Baseline = YGAlignBaseline,
   SpaceBetween = YGAlignSpaceBetween,
   SpaceAround = YGAlignSpaceAround,
+  SpaceEvenly = YGAlignSpaceEvenly,
 };
 
 template <>
 constexpr inline int32_t ordinalCount<Align>() {
-  return 8;
+  return 9;
 } 
 
 template <>
 constexpr inline int32_t bitCount<Align>() {
-  return 3;
+  return 4;
 } 
 
 constexpr inline Align scopedEnum(YGAlign unscoped) {