Properly log if the tags list has been truncated

🎱 Context

Follow up of !49961 (merged) where we added support for cleanup policies to truncate the list of tags to delete in order to lower the work pressure on the background workers and the container registry.

At that time, several logs have been added to the background worker message "done". This is to monitor the list truncation sizes.

Now we want to monitor closely when the list truncation happens. Unfortunately, we can't easily compare two fields in Kibana (compare the size before and after the truncation). To help with this, we're going to compute a boolean field that will indicate if the truncation happened or not.

This is a follow up of !49961 (merged) and doesn't need a changelog

Related to #288812 (closed)

🤔 What does this MR do?

• Add an additional log_extra_metadata_on_done field cleanup_tags_service_truncated in the ContainerExpirationPolicies::CleanupContainerRepositoryWorker.

📸 Screenshots (strongly suggested)

n / a

🛃 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
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