chore: add GH action for new client using hermetic build scripts

[diegomarquezp]

This PR enables new client generation using the hermetic build docker image.
It uses a combination of

• https://github.com/googleapis/google-cloud-java/blob/main/.github/workflows/verify-generation-config.yaml
• https://github.com/googleapis/google-cloud-java/blob/main/.github/workflows/generate_new_client.yaml

Steps

1. Calls a new script new_client_hermetic_build/new-client.py that adds an entry to generation_config.yaml with the specified arguments. The arguments are the 10 minimal arguments we find in https://github.com/googleapis/google-cloud-java/blob/main/.github/workflows/generate_new_client.yaml
2. Calls the hermetic build docker image to generate this specific library using the updated config yaml
3. Create a PR

Other changes

• It includes a reformat of a few libraries in generation_config.yaml

Demo PR

diegomarquezp#13