tools: show the launch stage of lagging APIs

[jskeet]

This just finds the launch stage from the service config, where it's present. (In many cases it's absent, but that's mostly historical.)

[gemini-code-assist]

Code Review

This pull request updates the ShowLaggingCommand to include the launch stage of lagging packages in its output by parsing service configuration YAML files from the googleapis repository. The review feedback recommends optimizing performance by deferring the GetLaunchStage call until after confirming a package is lagging, using standard string alignment instead of manual padding for the console output, and adding a file existence check to prevent potential exceptions during YAML parsing.

[gemini-code-assist]

Add a check to ensure the service configuration file exists before attempting to parse it. This prevents potential FileNotFoundException if the local googleapis repository is incomplete.

            var path = Path.Combine(googleapis, api.ProtoPath, api.ServiceConfigFile);
            if (!File.Exists(path))
            {
                return null;
            }
            var service = ApiAnalyzer.ParseServiceConfigYaml(path);

[jskeet]

Not done - if the file should exist but doesn't, it's better to fail so that the user can update their googleapis clone than silently not giving the output.