Update rubocop/gitlab-styles

What does this MR do?

Update gitlab-styles(rubocop update) and as a result:

• Use the now upstreamed CodeReuse/ActiveRecord version of the cop and remove the local.
• Introduce the .rubocop_manual_todo.yml file as a way to allow manually added exclusion lists to be preserved while they are worked on w/o causing manual work when auto regenerating the standard todo file.

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

Contributes to #259014