Migrate plugin to built-in Kotlin

[RafaelMarian]

I am using ffmpeg_kit_flutter_new_min_gpl 2.6.2 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.

Additional details

• Flutter 3.47
• Android Gradle Plugin 9.0.1
• Plugin version: ffmpeg_kit_flutter_new_min_gpl 2.6.2 (latest on pub.dev; changelog has no Built-in Kotlin migration)
• The published plugin still applies KGP in android/build.gradle:

apply plugin: com.android.library
apply plugin: kotlin-android

• Sibling variants (ffmpeg_kit_flutter_new 4.6.2, _min 3.6.2, _https_gpl 2.6.2, _full 2.5.2, _video) also have no published Built-in Kotlin release.
• Related: ffmpeg_kit_flutter_new_video Future versions of Flutter will fail to build if your app uses plugins that apply KGP. #168 reports the same Flutter warning for ffmpeg_kit_flutter_new_video. Open PR Migrate to built-in Kotlin #169 migrates master (full-gpl) only; the min-gpl branch / pub.dev package still applies kotlin-android.