Align text to the left by default in LTR on iOS

[YevheniiKotyrlo]

Summary:

Follow-up to #57634. A <Text> that declares no textAlign now aligns to the right in an RTL layout on iOS, but in an LTR layout its paragraph style still carries NSTextAlignmentNatural, which UIKit resolves against the app's localization rather than the paragraph (NSTextAlignment.natural: "the default alignment associated with the current localization of the app"). So when the app runs in a right-to-left language, text in an LTR subtree, such as a direction: 'ltr' view, is drawn flush right on iOS and flush left on Android.

RCTNSTextAttributesFromTextAttributes now resolves the alignment whenever the paragraph's layout direction is known, not only when it is RTL, so an undeclared alignment follows the start of the layout direction in both directions. RCTIsParagraphStyleEffectivelySame already compares a natural alignment as the start of the layout direction, so the drawn alignment now matches what it assumes. Text inputs are unaffected: their text attributes carry no layout direction, so a UITextField keeps aligning to its own view.

Changelog:

[IOS] [FIXED] - Align text to the left by default in LTR when textAlign is not set, whatever the app's language

Test Plan:

• RCTAttributedTextUtilsTest: testUndeclaredTextAlignmentResolvesWithLayoutDirection fails on main (an LTR paragraph gets no paragraph style) and passes with the change; testUndeclaredTextAlignmentWithoutLayoutDirectionStaysNatural passes on both. React-RCTFabric's Tests spec passes on an iOS 18.0 simulator, 56 tests with 0 failures, run with :testspecs => ['Tests'] and RCTParagraphComponentViewTests.mm excluded because it does not compile under CocoaPods.
• RNTester › Text › Text Align with RTL (direction: 'ltr', its initial state) on an iPhone 16 simulator, iOS 18.0, launched with Xcode's right-to-left pseudolanguage (-AppleTextDirection YES -NSForceRightToLeftWritingDirection YES), before and after: the pair. Only the two auto (default) lines move, from flush right to flush left; the left, center, right and justify lines are pixel-identical.
• node scripts/clang-format.js --check passes.

[YevheniiKotyrlo]

Device evidence — before / after

UNFIXED — under a right-to-left app language, the two auto (default) lines in this direction: 'ltr' box are drawn flush right.

FIXED — they are drawn flush left, the start of their layout direction; the declared left, center, right and justify lines do not move.

before — main at 1c6e0c7738	after — with this PR

iPhone 16 simulator, iOS 18.0, RNTester › Text › Text Align with RTL in its initial LTR state, launched with -AppleTextDirection YES -NSForceRightToLeftWritingDirection YES, one session. Only the rows of the two auto (default) lines differ: the English line's ink spans x 653–1176 before and 2–524 after, the Arabic line's 370–1176 and 2–808, of a 1179-px row.