CLI: Remove random commas in storybook upgrade logs

[joaonunomota]

Closes #22298

What I did

Log the stdout and stderr properties, instead of logging output property of result returned by npm-check-updates@latest.

This provides the following benefits:

• Avoids commas that come from logging an array, which solves [Bug]: some extra comma #22298.
• It is clearer in the code what is being logged, since stdout and stderr are equal to output[1] and output[2] respectively.
• stderr can be logged at a different level to stdout (not sure what the rule for using info or warn on logs)

It also:

• Does not log output[0] which in this case is null.
• Adds an extra newline between stdout and stderr logs

An example of what the logs look like before and after with some forced warnings (using reproduction code):

How to test

1. Run a sandbox for template, e.g. yarn task --task sandbox --start-from auto --template react-vite/default-ts
2. Run npx storybook@latest upgrade
3. Observe logs, specifically for npm-check-updates

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[JReinhold]

Thanks for this! 💪