Move typdef from RCTImageView -> RCTUIKit

[Saadnajmi]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

This came up while resolving conflicts in the 0.71 merge.
Move a typedef associated with UIImage to the macOS part of RCTUIKit. Once done, we can remove a #if !TARGET_OS_OSX if/else block, since #import <React/RCTUIKit.h> will bring in either Appkit or UIKit based on the platform.

Changelog

[macOS] [Changed] - Move typdef from RCTImageView -> RCTUIKit

Test Plan

CI should pass

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: 2217ea4
Branch: main