Add CodeQuality sample configuration for private image registries

What does this MR do?

This merge request adds documentation for configuring CodeQuality to not use Dockerhub. Using a private registry to host open-source images has been a consistent feature request from large organizations, and it became much more important since Dockerhub implemented rate limits for pulls.

The configuration described here is currently being used by a relatively large SaaS customer, who has reported back that they are completely avoiding pulls from Dockerhub, and do not need to maintain any sort of contract with Dockerhub to enable their use of the CodeQuality template and project.

Documenting this explicitly should lower the barrier to success for more customers going forward.

Related issues

Original issue: #283929 (closed)

Author's checklist

• Follow the Documentation Guidelines and Style Guide.
• Ensure that the product tier badge is added to doc's h1.
• Request a review based on the documentation page's metadata and associated Technical Writer.

To avoid having this MR be added to code verification QA issues, don't add these labels: feature, frontend, backend, ~"bug", or database

Review checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
• Ensure a release milestone is set.