feat: add custom prompt config in the request and return prompt in the response#32298

gcf-owl-bot[bot] wants to merge 4 commits intomaingoogleapis/google-cloud-ruby:mainfrom

owl-bot-copy-google-cloud-alloy_db-v1betagoogleapis/google-cloud-ruby:owl-bot-copy-google-cloud-alloy_db-v1betaCopy head branch name to clipboard