[flutter_local_notifications] Add CarPlay notification support with IOSInitializationSettings

[derrik-fleming]

Closes #2715

Summary

• Introduces IOSInitializationSettings class for iOS-specific notification features including CarPlay support
• Adds CarPlay notification permission request capability via requestCarPlayPermission parameter
• Maintains full backward compatibility with existing DarwinInitializationSettings usage

Changes Made

Core Implementation

• New class: IOSInitializationSettings extends DarwinInitializationSettings
• CarPlay support: Added requestCarPlayPermission parameter for iOS 10.0+ devices
• Permission checking: Extended NotificationsEnabledOptions with isCarPlayEnabled status
• Platform mapper: Created iOS-specific mapper that includes CarPlay permissions

Native iOS Changes

• Added CarPlay permission constants and handling in FlutterLocalNotificationsPlugin.m
• Implemented CarPlay authorization option support (UNAuthorizationOptionCarPlay)
• Added CarPlay status checking in permission verification

Testing & Documentation

• Comprehensive test coverage for new IOSInitializationSettings class
• Updated integration tests to use IOSInitializationSettings
• Added migration examples and CarPlay usage documentation
• Updated iOS deployment target to 13.0 for example app

Backward Compatibility

• Existing code using DarwinInitializationSettings continues to work unchanged
• Runtime type checking ensures appropriate mapper usage
• CarPlay permissions excluded when using DarwinInitializationSettings

[MaikuB]

Thanks for the PR. I left some comments and can also see some checks have failed. Would you be able to take a look?

[MaikuB]

Thanks I didn't realise you had made updates to resolve issues as I saw one comment was left open but turns out it was addressed too. There's now conflicts after I merged PRs having not known this was ready. I raised a PR to your fork as it looks like the setting to allow maintainers to edit wasn't ticked Gentex-Corporation#1