refactor/Convert object to data object in sealed interface

[KDW03]

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By leveraging the data object feature introduced and stabilized in Kotlin version 1.9.0, this refactor will provide a more descriptive toString() representation, ensuring a uniform approach to defining states across sealed interfaces and enhancing the debuggability with the improved toString() method.

Fixes #998

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• Run local tests on DemoDebug variant: ./gradlew testDemoDebug
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• Run ./tools/setup.sh
• Import the code formatting style as explained in the setup script.

[dturner]

Thanks very much for doing this.