This further improves the `KotlinCompositeProvider` abstraction:
- Pulling the abstraction's interfaces outside the `impl` package allows
us to write consolidated documentation on composable Kotlin providers.
- The addition of `KotlinComposableProvider` allows more specific bounds
for the type parameters of `KotlinCompositeProvider` and
`KotlinCompositeProviderFactory`. It also clarifies to Analysis API
implementors which providers can be composed at all, as providers like
`KotlinDeclarationProvider` extend this interface.
- `KotlinComposableProviderMerger` provides a unified interface for
provider mergers.
^KT-61791
Marco Pennekamp
a62ac940c4