Fixed text background color

Summary:
@public

This fixes an issue with the containerBackgroundColor property of `<Text>` nodes, where containerBackgroundColor was being overridden by the backgroundColor. I also fixed up the example so that it demonstrates the feature more clearly.

Test Plan:
* Check UIExplorer text example
* Run Catalyst snapshot tests and check MAdMan, Groups

React/Base/RCTConvert.m

@@ -916,10 +916,10 @@ static id RCTConvertPropertyListValue(id json)
   return RCTConvertPropertyListValue(json);
 }
 
-RCT_ENUM_CONVERTER(css_overflow, (@{
-  @"hidden": @NO,
-  @"visible": @YES
-}), YES, boolValue)
+RCT_ENUM_CONVERTER(css_clip_t, (@{
+  @"hidden": @YES,
+  @"visible": @NO
+}), NO, boolValue)
 
 RCT_ENUM_CONVERTER(css_flex_direction_t, (@{
   @"row": @(CSS_FLEX_DIRECTION_ROW),