[zoontek]

Summary:

On iOS, an RTL horizontal ScrollView is mirrored, so its UIKit offset counts from the right edge. scrollTo and onScroll converted it, but the contentOffset prop and ScrollViewState did not. As a result, measure returned wrong x values (#55153), and the prop and scrollTo showed different pages (#58534).

Offsets now count from the left edge everywhere on iOS, like Android. Android code paths are unchanged.

Fixes #55153
Fixes #58534

Changelog:

[IOS] [FIXED] - Fix measure, measureInWindow and the contentOffset prop in RTL horizontal ScrollView

Test Plan:

Added two RNTester examples under ScrollView, "in RTL measure" and "in RTL contentOffset". Ran them on the iOS simulator:

Case	Before	After
measureInWindow x (button at 46)	-434	46
contentOffset={{x: 600}} vs scrollTo({x: 600})	Page 3 vs Page 2	Page 2 for both

[github-actions]

Visual regression

No visual differences at 8afc813fb34d.

android: no capture