Kotlin/Native: Swift Build integration and KMP → SwiftPM conversion

[rbbozkurt-jb]

This PR introduces a proof-of-concept integration of Kotlin/Native into Swift Build, allowing Swift targets to depend on Kotlin targets. Kotlin sources are compiled into .klib artifacts and exposed to Swift through an auto-generated KotlinWorld.framework.

Context / motivation:

• SwiftPM and Xcode target models currently do not support Kotlin/Native as a first-class language/toolchain.
• This change explores how Swift Build can detect Kotlin sources, schedule Kotlin compilation in the build graph, propagate Kotlin-to-Kotlin dependencies transitively, and generate a framework that Swift targets can import and link against.
• It also includes a prototype Gradle-based KMP → SwiftPM conversion workflow and sample projects demonstrating SwiftPM and Xcode usage.