Migrate plugin to built-in Kotlin #619

I am using record_android in my Flutter app.

Starting with Android Gradle Plugin (AGP) 9.0, support for applying the Kotlin Gradle Plugin (KGP) has been removed. Because this plugin applies KGP, it causes a compilation error that prevents my app from building. Flutter issue #181383 includes an example of the error.

Flutter has temporarily added support to allow KGP while apps and plugins migrate to AGP 9.0 or later, but this support will be removed in a future version of Flutter.

Please migrate this plugin to use built-in Kotlin to ensure your plugin users can successfully build their apps in future versions of Flutter.

Here is the Flutter migration guide for plugin authors: https://docs.flutter.dev/release/breaking-changes/migrate-to-built-in-kotlin/for-plugin-authors.