[iOS] Respect user numeric format overrides

[matouskozak]

Fixes #110430

Summary

• create dedicated user-default culture data for Apple Hybrid Globalization
• use NSLocale.currentLocale for overrideable locale values while keeping named cultures identifier-based
• add Apple mobile regression coverage for current and named culture number formats
• preserve PredefinedCulturesOnly validation for the user-default locale

Testing

• ./build.sh mono+libs -os iossimulator -arch arm64
• CurrentCultureTests on the iOS simulator: 9 passed, 0 failed
• Runtime iOS sample: decimal.TryParse("1,23") changed from 123 to 1.23 with the device override

Note

This pull request description was generated with GitHub Copilot.

[Copilot]

Pull request overview

This PR updates Apple Hybrid Globalization so the user-default culture can reflect iOS “Numeric Format” overrides (e.g., decimal/group separators) by switching relevant native locale lookups to use NSLocale.currentLocale when user overrides are enabled.

Changes:

• Plumbs a useUserOverride flag through Apple-hybrid native locale info entrypoints and corresponding managed LibraryImport declarations.
• Creates a dedicated “user default” CultureData path on Apple mobile Hybrid mode and uses it to construct CultureInfo.CurrentCulture.
• Adds Apple mobile regression tests asserting current vs named culture number format behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/native/libs/System.Globalization.Native/pal_localeStringData.h	Adds useUserOverride parameter to Apple-hybrid string locale info export.
src/native/libs/System.Globalization.Native/pal_localeNumberData.h	Adds useUserOverride parameter to Apple-hybrid numeric/grouping locale info exports.
src/native/libs/System.Globalization.Native/pal_locale.m	Introduces GetNativeLocale helper using currentLocale when overrides are requested; threads the flag through native exports.
src/libraries/Common/src/Interop/Interop.Locale.iOS.cs	Updates managed LibraryImport signatures to include useUserOverride (marshalled as UnmanagedType.Bool).
src/libraries/System.Private.CoreLib/src/System/Globalization/CultureInfo.Unix.cs	Uses a new Apple-hybrid user-default CultureData creation path for CurrentCulture.
src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.iOS.cs	Adds GetUserDefaultCultureData and threads useUserOverride to native locale info calls.
src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.cs	Ensures Apple-hybrid “user override” locale queries consult _bUseOverrides when calling into native.
src/libraries/System.Runtime/tests/System.Globalization.Tests/CultureInfo/CultureInfoCurrentCulture.cs	Adds Apple mobile tests for current vs named culture number separators.

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