feat(librarian/nodejs): add additional_protos support

[quirogas]

Implement a robust mechanism for including additional proto dependencies during Node.js client generation. It introduces the additional_protos configuration field and implements a union logic with common resources.

Implementation Details

• Added AdditionalProtos to the NodejsPackage and NodejsAPI config structs.
• Default Behavior: Librarian automatically includes google/cloud/common_resources.proto by default for all Node.js APIs. This provides out-of-the-box support for common path templates without requiring manual configuration for most libraries.
• Union Logic: Specifying additional_protos (at the package or API level) allows adding extra dependencies. These are appended to the default common_resources.proto and deduplicated.
• Naming Consistency: Follows the pattern established in the Java generator for naming and YAML tags.

Verification

• Verified against google-cloud-secretmanager, google-cloud-kms, and google-cloud-resourcemanager.
• Functional parity achieved: projectPath and related helpers are correctly restored in the generated clients.
• Unit tests added in internal/librarian/nodejs/generate_test.go covering default, hierarchical union, and deduplication scenarios.

---

Fix #5208: Provides the necessary infrastructure to include google/cloud/common_resources.proto, which contains common path template definitions.

Fix #4744: Directly resolves the problem where the Node.js generator removes path template helpers (like projectPath) by ensuring the required resource definitions are available to protoc.

For #4404: Updates the Node.js generation logic to support these new configuration fields.

For #4413: The migrate tool should be updated to automatically detect proto_library_with_info dependencies from BUILD.bazel files and populate the additional_protos field in librarian.yaml.

[gemini-code-assist]

Code Review

This pull request enables Node.js-specific API configurations, allowing for the inclusion of extra proto files during client library generation. It adds a NodejsAPIs field to the configuration and a resolution helper that defaults to common_resources.proto. Feedback suggests appending user-provided protos to the default list rather than overwriting it, ensuring that essential resources for path helper methods are always preserved.

[sofisl]

generally speaking one thing I'm not super clear on in Librarian is how it actually will get rid of Bazel files. But regardless, I think some test you want to set up is something to confirm that those necessary protos specified in the BUILD.bazel are actually passed in correctly. (maybe that's in another PR I assume)?

Not sure if this is more generally helpful, but this is what I mean by those extra necessary protos: cl/582493526. When I added compileProtos to the generation step (techncially outside of the generator, running in a wrapper script), I had to specify a bunch of these protos to actually get the code to run.