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 in this PR. @danieljbruce and I were trying out selective gapic with bigtable admin, and we attempted to generate a new library with this file. 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.