Move toolchain helpers into a separate private file. After the migration those should be removed, so let's not make it a new public APIs. Copybara also handles differences in toolchain type labels.
Remove ProtoLangToolchainInfo from proto_common. Providers need special care when moving and will be moved last.
Read INCOMPATIBLE_ENABLE_PROTO_TOOLCHAIN_RESOLUTION from native proto_common. This is a BuildLanguageConfiguration flag (load time flag) and may only be read through native support. Add a dependency to the latest bazel_features that supports this check. On older Bazel versions fail if ALLOWLIST is configured.
Implement version check for PackageSpecificationInfo. It's only available after Bazel 6.4.0.
The rest of the implementation matches Bazel version. Tests are quite extensive and will be submitted in separate PRs.
PiperOrigin-RevId: 651699412
Protobuf Team Bot