KSP: use KSP to generate ViewModel boilerplate code

[kaushikgopal]

This PR aims to use KSP to generate the boilerplate code needed for the FeatureVM class. The way the UDF model works here is that you just write the code for the FeatureVMImpl with the event → result → state/effect transformations and KSP takes care of the rest.

• UsfViewModelProcessor has the interesting code and implements SymbolProcessor that processes all objects annotated with @UsfViewModel
• In order to register this you need to provide a SymbolProcessorProvider file and register it in your MANIFEST/services directory
• The goal is to have MSMovieVM generated automatically from MSMovieVMImpl by just annotating MSMovieVMImpl with @UsfViewModel

Many thanks to @CubanAzcuy for help with this 🙏🏽

[kaushikgopal]

Refactored generated ViewModel: no longer implements UsfVm interface, simplifying KSP logic. This change is transparent from an API user perspective. Future modifications may bring KSP generation code closer to this approach.

@CubanAzcuy was not comfortable with some of the hard-coding that was required in the ksp gen code, to enable the implementation of the interface.