Add initial support for Kotlin Native toolchain and klib compilation

[smocherla-brex]

In #1347 (comment), it was mentioned that it's preferred to bootstrap a Kotlin native toolchain first to leverage the new IR compiler to utilize a compilation model to output klibs in a generic way that can be leveraged for JS and potentially other platforms in the future. This PR tries to add that to the toolchain and also adds a new rule kt_klib_library rule which is intended to use the Kotlin-native compiler to produce klibs for platform indepedent code that can be shared between various platform specific targets (think of commonMain in a gradle project) and can be in the future consumed by platform specific JS/JVM (and maybe WASM targets as well).

Some notes on the implementation details:

1. I had to write a repository rule kotlin_native_compiler_repository to bootstrap/download the native distributions for different platforms supported along with its "capabilities" repository similar to how kotlinc is setup. I'll add some more comments inline.
2. Make sure to expose konan.home or the native compiler files as a TreeArtifact/directory to avoid passing a massive number of files during compilation.
3. Pass the relevant flags during klib compilation with its own task executor with key ones being produce=library
4. Additionally, expose alias targets like //kotlin/compiler:kotlin-native which is supposed to alias to the native compiler jar/distribution on the execution platform.
5. Add examples for simple one (using stdlib) and one with deps (kt_klib_library depending on another target). Add some junit test cases to assert klib has some entries we expect.
6. Add a few starlark unit test cases.

A simple example shown below:

smocherla@NLC2L54QQY rules_kotlin_oss % bazel build //src/test/data/klib:deps_main
WARNING: For repository 'com_google_protobuf', the root module requires module version protobuf@29.0, but got protobuf@29.3 in the resolved dependency graph.
WARNING: For repository 'rules_python', the root module requires module version rules_python@0.23.1, but got rules_python@0.37.2 in the resolved dependency graph.
INFO: Analyzed target //src/test/data/klib:deps_main (280 packages loaded, 33903 targets configured).

[1,205 / 1,207] Compiling Kotlin to Klib //src/test/data/klib:deps_greeting { kt: 1 }; 3s worker
Target //src/test/data/klib:deps_main up-to-date:
  bazel-bin/src/test/data/klib/deps_main.klib
INFO: Elapsed time: 110.427s, Critical Path: 39.07s
INFO: 1207 processes: 582 internal, 604 darwin-sandbox, 

TODO:

• Fix some of the integration test failures
• Decide if a separate rule is needed for klibs or fit it into existing platform-specific rules.

[smocherla-brex]

I added this to leverage copy_to_directory to expose the Kotlin native compiler distribution as a directory in the toolchain here (as it's massive and has a ton of files)

[smocherla-brex]

This is the new kt_klib_library rule that produces klibs using the kotlin/native toolchain. Potentially we could just have it as action and have an attr on the existing rules to trigger klib compilation on them as well (I'm not sure if that's better - let me know)

[smocherla-brex]

Without this, the compiler tries to write within the cache in the external repository where konan.home is and bazel errors out. Ideally we disable caching but there doesn't seem to be a flag for this.

[smocherla-brex]

This is needed for the compiler to find the native code/distribution to produce klib.

[smocherla-brex]

This was copied into a separate file to allow leveraging it with kotlin_native_compiler_repository

[smocherla-brex]

The compiler on bootstrap tries to create klib/cache/<platform>STATIC directory in the external repo and this is non-hermetic and causes Bazel to fail. To workaround it (unfortunately there doesn't appear to be a way to disable it with a flag), so we create this marker/dummy file to avoid running into the issue (happy to consider other solutions)