Refactor code in PruneOldEventsWorker & PruneWebHookLogsWorker

What does this MR do?

This is an extension to the work done in !23854 (merged).

This involves:

• Moving delete_with_limit to a concern, so that it can be reused in 3 different places now.
• Refactor code in PruneOldEventsWorker & PruneWebHookLogsWorker to make use of the new DeleteWithLimit concern.
• Also make use of the created_before method already available in CreatedAtFilterable, so that we can completely get rid of disabling the CodeReuse/ActiveRecord cop 👮

Screenshots

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