feat: improve animating colors (#2471)

# Summary

Currently on Fabric, you cannot animate color properties like `fill` or
`stroke` using Animated with `useNativeDriver: true` or Reanimated.
That's because we have custom structure that needs to be parsed on `JS`
and looks like:

```ts
type ColorStruct = Readonly<{
  type?: WithDefault<Int32, -1>;
  payload?: ColorValue;
  brushRef?: string;
}>;
```

However, special values like `currentColor` / `context-fill` /
`context-stroke` / `/^url\(#(.+)\)$/` can not be animated anyway.
Instead, we should allow passing `ColorValue` directly and detect on the
native side if its ColorValue or ColorStruct.

## Test Plan

Example app -> TestX

## Compatibility

| OS      | Implemented |
| ------- | :---------: |
| iOS     |    ✅      |
| MacOS   |    ✅      |
| Android |    ✅      |

## Checklist

- [x] I have tested this on a device and a simulator
- [ ] I added documentation in `README.md`

apple/Utils/RNSVGFabricConversions.h

@@ -55,38 +55,6 @@ static id RNSVGConvertFollyDynamicToId(const folly::dynamic &dyn)
   }
 }
 
-template <typename T>
-RNSVGBrush *brushFromColorStruct(const T &fillObject)
-{
-  int type = fillObject.type;
-
-  switch (type) {
-    case -1: // empty struct
-      return nil;
-    case 0: // solid color
-    {
-      // These are probably expensive allocations since it's often the same value.
-      // We should memoize colors but look ups may be just as expensive.
-      RNSVGColor *color = RCTUIColorFromSharedColor(fillObject.payload) ?: [RNSVGColor clearColor];
-      return [[RNSVGSolidColorBrush alloc] initWithColor:color];
-    }
-    case 1: // brush
-    {
-      NSArray *arr = @[ @(type), RCTNSStringFromString(fillObject.brushRef) ];
-      return [[RNSVGPainterBrush alloc] initWithArray:arr];
-    }
-    case 2: // currentColor
-      return [[RNSVGBrush alloc] initWithArray:nil];
-    case 3: // context-fill
-      return [[RNSVGContextBrush alloc] initFill];
-    case 4: // context-stroke
-      return [[RNSVGContextBrush alloc] initStroke];
-    default:
-      RCTLogError(@"Unknown brush type: %d", type);
-      return nil;
-  }
-}
-
 template <typename T>
 void setCommonNodeProps(const T &nodeProps, RNSVGNode *node)
 {
@@ -143,10 +111,16 @@ void setCommonRenderableProps(const T &renderableProps, RNSVGRenderable *rendera
   if (RCTUIColorFromSharedColor(renderableProps.color)) {
     [renderableNode setColor:RCTUIColorFromSharedColor(renderableProps.color)];
   }
-  renderableNode.fill = brushFromColorStruct(renderableProps.fill);
+  id fill = RNSVGConvertFollyDynamicToId(renderableProps.fill);
+  if (fill != nil) {
+    renderableNode.fill = [RCTConvert RNSVGBrush:fill];
+  }
   renderableNode.fillOpacity = renderableProps.fillOpacity;
   renderableNode.fillRule = renderableProps.fillRule == 0 ? kRNSVGCGFCRuleEvenodd : kRNSVGCGFCRuleNonzero;
-  renderableNode.stroke = brushFromColorStruct(renderableProps.stroke);
+  id stroke = RNSVGConvertFollyDynamicToId(renderableProps.stroke);
+  if (stroke != nil) {
+    renderableNode.stroke = [RCTConvert RNSVGBrush:stroke];
+  }
   renderableNode.strokeOpacity = renderableProps.strokeOpacity;
   id strokeWidth = RNSVGConvertFollyDynamicToId(renderableProps.strokeWidth);
   if (strokeWidth != nil) {