chore: upgrade to kotlin 2.0.20

[DominicGBauer]

Description

Kotlin 2.0.20 is out and fixes issues related to using Kotlin with XCode 16 which has required us upgrading from 1.9.24.

Work Done

• Needed to add and use new compose compiler plugin (https://www.jetbrains.com/help/kotlin-multiplatform-dev/compose-compiler.html#migrating-a-compose-multiplatform-project)
• Removed kotlinCompilerExtensionVersion from hello-powersync as this is no longer required (https://android-developers.googleblog.com/2024/04/jetpack-compose-compiler-moving-to-kotlin-repository.html)
• Needed to move to SKIE 0.9.0-RC5 as this supports Kotlin 2.0.20
• Removed unused dependencies
• hello-powersync required a gradle upgrade to 8.7 in order to run
• Git Ignored .kotlin folders
• Changed from api to implelementation where possible in demos

Testing

1. Ran both supabase-todolist and hello-powersync demos in Android and iOS and confirmed they still run
2. Created a new XCFramework for PowerSync Swift SDK and used that in the Swift Kotlin Demo app

[DominicGBauer]

@stevensJourney I've confirmed upgrading to core to Kotlin 2 does not affect apps that are using a lower version of Kotlin. I downgraded supabase-todolist and removed all the new requirements to confirm this.