Extract ProjectStatistics updates into a concern

What does this MR do?

This MR is extracting refactoring from !27373 (merged) for an easier review.

Both Ci::Build and Ci::JobArtifact are implementing the same logic to invoke ProjectStatistics.increment_statistic.

This MR extracts such duplicated logic into the new UpdateProjectStatistics concern. Also duplicated tests are extracted into shared examples.

In order to show group level storage counters (#59232 (closed)), we need to keep track of storage used for the Package features, and it's time to fix this duplication.

Does this MR meet the acceptance criteria?

Conformity

• [-] ~backstage Changelog entry not needed
• [-] ~backstage Documentation created/updated or follow-up review issue created not needed
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance 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

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