Suppress RuboCop output when there are no offenses in code generation

[koic]

Motivation / Background

Follow up #51782.

But it's overkill for the default case where people use the default style guide,
and it introduces both delay and console output as a cost.

Detail

When there are no offenses with the coding style generated by code generation, outputting RuboCop results to the console was redundant. Since RuboCop has --format=quiet option that suppresses console output when there are no offenses, this PR adds that option: https://docs.rubocop.org/rubocop/1.63/formatters.html#quiet-formatter

While this PR doesn't resolve any added execution speed by RuboCop, the frequency of using the generator is not high within the development flow. Therefore, depending on the execution speed, it might be possible to uncomment #51782, but this PR respects the defaults in #51782 and doesn't address that.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.