feat(bigtable): split gapic and proto usage from the handwritten library into bigtable-api

[feywind]

This is in the effort to remove OwlBot from the standard repo path. A new package (bigtable-api) takes care of what OwlBot used to do (shuffle in new protos and generated gapic classes).

Internal: b/531788771

[gemini-code-assist]

Code Review

This pull request refactors the codebase to depend on the external @google-cloud/bigtable-api package for API clients and proto definitions, allowing the removal of numerous auto-generated client files, configurations, and shims. Feedback on the changes highlights a critical issue in handwritten/bigtable/src/admin/table.ts where JSON_PROTOS is read as a raw string using fs.readFileSync instead of being parsed as a JSON object, which will cause runtime failures in protobufFromJSON. A suggestion is provided to use require to synchronously load and parse the JSON file directly.

[feywind]

The PR might be a bit gross until I debug the resource leaks.

[quirogas]

PR looks good to me, Let's open follow up clean up bugs for:

• removing proto files and addressing test_proxy.proto
• cleanup tests, specially tests that depend on proto files
• transition to the .json definition of the service file as opposed to using the proto files.
• remove logs
• split test changes into a separate PR.
• remove utility script from publishing (if not already)

Feel free to reference this commnet to create the issues initially or create new ones altogether, up to you.

[quirogas]

Can we delete this file or directory altogether and add the export logic to the index.ts file in the parent directory?

[quirogas]

Same as admin/v2/index.ts. Could we move this export to the top-level file instead?