Find project_authorizations records due for refresh via a service class [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

This is the first step towards implementing #292443 (closed)

Currently, we have a service class named Users::RefreshAuthorizedProjectsService, which performs the dual function of

• finding the records that should be added or removed.
• Adding or removing these specific records in ProjectAuthorizations table.

With this MR, a new service class named AuthorizedProjectUpdate::FindRecordsDueForRefreshService is being added which performs the function of

• finding the records that should be added or removed.

The pros of this approach is

• Responsibilities are now split
• Users::RefreshAuthorizedProjectsService further calls AuthorizedProjectUpdate::FindRecordsDueForRefreshService to obtain the records that needs removal or addition.
• AuthorizedProjectUpdate::FindRecordsDueForRefreshService is now standalone, and only performs "read" queries, which means we can use this service in a standalone manner towards accomplishing #292443 (closed) (For a detailed plan on how this new class will be used in a standalone manner, please see !54836 (comment 515219453))

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this is only a refactor.
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
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