Migrate to injectable warning features in score_bazel_cpp_toolchains

## What

Migrate Baselibs to the newest `score_bazel_cpp_toolchains` and use the injectable warning features introduced in [score_cpp_policies#33](https://github.com/eclipse-score/score_cpp_policies/pull/33) for the GCC and LLVM toolchains.

This centralizes warning policy configuration, keeps both toolchains aligned, and lets Baselibs benefit from shared policy updates.

## Toolchain configuration

Inject selectable warning features with `extra_known_features` and default-enabled warning features with `extra_enabled_features` in each toolchain configuration.

## Acceptance Criteria (DoD)

- [ ] Baselibs uses the newest compatible `score_bazel_cpp_toolchains` version.
- [ ] The GCC toolchain uses the injectable warning features from `score_cpp_policies`.
- [ ] The LLVM toolchain uses the injectable warning features from `score_cpp_policies`.

Start by locating the dependency declaration for score_bazel_cpp_toolchains and the GCC and LLVM toolchain configurations in the repository. Check the newest compatible version and compare each configuration with the injectable warning features from score_cpp_policies; done means both toolchains use the requested features and the acceptance criteria are satisfied.

Written by the indexing model from the issue text.