Auto approve users if Admin approval after sign up setting is disabled

What does this MR do?

This MR calls the ApproveBlockedPendingApprovalUsersWorker when the require_admin_approval_after_user_signup setting is disabled by the admin. The worker will call the Users::ApproveService for all users in blocked_pending_approval state.

📣 This MR also moves the worker outside ee/ and modifies the methods in EE::ApplicationSettings::UpdateService since both services now use the same worker.

❗ This change is targeted to SM instances only.

Second part of #273258 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• 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.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team