Refactor Geo::VerifiableRegistry module

What does this MR do?

• Nest the module, see #39044 (closed)
• Include VerificationState in VerifiableRegistry, see #298811 (closed). VerifiableRegistry depends on VerificationState anyway, and I don't know why I had trouble doing this earlier.

Resolves #298811 (closed)

Does this MR meet the acceptance criteria?

Conformity

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  • I have included a changelog entry.
  • I have not included a changelog entry because it is a refactor.
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• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.