[flutter_local_notifications] - Updating the desugaring dependency to support JAVA 21 builds and cleanup on podfile

[dishankjindal1]

1. Added support for JAVA 21 builds.
2. Cleanup on ios files and podfile to update it to latest flutter standards formatting and structures.

ps: I was working on enabling JAVA 21 as it is officially supported by flutter from the latest v3.27.3. so after making current changes build is getting compiled properly. and i also tested this same code in my old projects it is not breaking any old projects.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[MaikuB]

Thanks for the PR. Could you split the PR into two separate ones? Putting that aside, happy to take changes to do with the example app on the iOS side but what exactly are you trying to fix on the Android side? I'm not aware of issues with Java 21. The issues I've seen to do with Java 21 and Flutter had been to do with AGP. I was able to build and run the example app locally without your changes. I also created a branch where the pipeline is made to use Java 21 and it compiles fine too. You can see the output at https://github.com/MaikuB/flutter_local_notifications/actions/runs/13212896584/job/36888650465

[dishankjindal1]

Will raise new seperate PRs.

[MaikuB]

FYI I need to fix some issues with example app will be incorporating the example app updates on iOS side as part of this