Integrate new credentials step for automated migrations

[renatho]

Details

Check the current status of the new step with credentials, and if it's done integrate it in the new flow instead of the site-migration-source-url.

See the new step being introduced: #93339

Checklist

• Checked if the new step is ready for use.
• Replaced site-migration-source-url with the new step introduced in Automated Migrations: Add the Credentials collection placeholder step #93339.

Related

#93304

[renatho]

#94024