Selective gapic generation is broken

I think the selective gapic generation isn't quite working, and in order to confirm we should add a full test that reads from an actual service config file, like [this](https://github.com/googleapis/gapic-generator-typescript/blob/db273cfd91e1326201f5dda222258f12e0d5669a/test-fixtures/protos/google/showcase/v1beta1/showcase_v1beta1.yaml) in [this PR](https://github.com/googleapis/gapic-generator-typescript/pull/1511/files). @danieljbruce and I were trying out selective gapic with bigtable admin, and we attempted to generate a new library with [this file](https://paste.googleplex.com/5141699252453376). The outcome of the generation was that only a single method was listed internal, `RestoreTableMetadata`. This seems wrong since we listed a bunch of methods to be internal, but I also am not very familiar with the logic behind what gets generated or not.

Also, we had to change the `settings` property from `node_settings` to `typescript_settings` to get anything to produce, which is not how the service_yaml file is set up (it should be `node_settings`). I think this is a bug in the generator implementation.