Move `[RCTConvert RCTTransformOrigin:]` out of UIAccessibilityTraits category (#39758)

Summary:
5f40f0800e added a new prop and corresponding RCTConvert method for transformOrigin. Strangely, it added the RCTConvertMethod to a `RCTConvert+UIAccessibilityTraits` category.. which feels like the wrong spot for it. Let's just add it to the existing `RCTConvert+Transform` category. This also means we can get rid of the header if we move the `RCTTransformOrigin` struct into UIView+React (where it is used).

## Changelog:

[IOS][CHANGED] - Move `[RCTConvert  RCTTransformOrigin:]` out of UIAccessibilityTraits category

Pull Request resolved: https://github.com/facebook/react-native/pull/39758

Test Plan:
Transform Origin example still works.
<img width="559" alt="Screenshot 2023-10-02 at 11 26 17 AM" src="https://github.com/facebook/react-native/assets/6722175/c7b863cc-3595-430d-8579-f8ce8e73c4f4">

Reviewed By: javache

Differential Revision: D49867993

Pulled By: NickGerleman

fbshipit-source-id: 1b2d5a9d08f0231040e7449f2eb75860f08bafa5

packages/react-native/React/Views/RCTConvert+Transform.h

@@ -6,9 +6,12 @@
  */
 
 #import "RCTConvert.h"
+#import "UIView+React.h"
 
 @interface RCTConvert (Transform)
 
 + (CATransform3D)CATransform3D:(id)json;
 
++ (RCTTransformOrigin)RCTTransformOrigin:(id)json;
+
 @end

packages/react-native/React/Views/RCTConvert+Transform.m

@@ -144,4 +144,11 @@ static const NSUInteger kMatrixArrayLength = 4 * 4;
   return transform;
 }
 
++ (RCTTransformOrigin)RCTTransformOrigin:(id)json
+{
+  RCTTransformOrigin transformOrigin = {
+      [RCTConvert YGValue:json[0]], [RCTConvert YGValue:json[1]], [RCTConvert CGFloat:json[2]]};
+  return transformOrigin;
+}
+
 @end

packages/react-native/React/Views/RCTTransformOrigin.h

@@ -1,15 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-#import <Foundation/Foundation.h>
-#import <yoga/Yoga.h>
-
-typedef struct {
-  YGValue x;
-  YGValue y;
-  CGFloat z;
-} RCTTransformOrigin;

packages/react-native/React/Views/RCTViewManager.m

@@ -15,7 +15,6 @@
 #import "RCTConvert.h"
 #import "RCTLog.h"
 #import "RCTShadowView.h"
-#import "RCTTransformOrigin.h"
 #import "RCTUIManager.h"
 #import "RCTUIManagerUtils.h"
 #import "RCTUtils.h"
@@ -122,13 +121,6 @@ RCT_MULTI_ENUM_CONVERTER(
     UIAccessibilityTraitNone,
     unsignedLongLongValue)
 
-+ (RCTTransformOrigin)RCTTransformOrigin:(id)json
-{
-  RCTTransformOrigin transformOrigin = {
-      [RCTConvert YGValue:json[0]], [RCTConvert YGValue:json[1]], [RCTConvert CGFloat:json[2]]};
-  return transformOrigin;
-}
-
 @end
 
 @implementation RCTViewManager

packages/react-native/React/Views/UIView+React.h

@@ -8,11 +8,17 @@
 #import <UIKit/UIKit.h>
 
 #import <React/RCTComponent.h>
-#import <React/RCTTransformOrigin.h>
+#import <React/RCTConvert.h>
 #import <yoga/YGEnums.h>
 
 @class RCTShadowView;
 
+typedef struct {
+  YGValue x;
+  YGValue y;
+  CGFloat z;
+} RCTTransformOrigin;
+
 @interface UIView (React) <RCTComponent>
 
 /**