Implement RCTTextInlineImage with Nodes

Summary:
React allows nesting <Image> inside <Text>, in which case it turns into an RCTTextInlineImage element. RNFeed is using it in a few places and thus we need to support it, too.

This diff implements it with InlineImageSpan (WithPipeline, and WithDrawee separately).

Reviewed By: ahmedre

Differential Revision: D2792569

ReactAndroid/src/main/java/com/facebook/react/flat/RCTVirtualText.java

@@ -59,6 +59,14 @@ import com.facebook.react.uimanager.ViewProps;
     }
   }
 
+  @Override
+  protected void performCollectAttachDetachListeners(StateBuilder stateBuilder) {
+    for (int i = 0, childCount = getChildCount(); i < childCount; ++i) {
+      FlatTextShadowNode child = (FlatTextShadowNode) getChildAt(i);
+      child.performCollectAttachDetachListeners(stateBuilder);
+    }
+  }
+
   @ReactProp(name = ViewProps.FONT_SIZE, defaultFloat = Float.NaN)
   public void setFontSize(float fontSizeSp) {
     final int fontSize;