Aggregate push events when there are too many

What does this MR do?

Implements the functionality to aggregate push events as one push event when number of changes for branches and tags in a single push exceeds 3 (by default, configurable via push_event_activities_limit).

This way, if there are a lot of changes in a single push (e.g. 10000 branches/tags), we won't need to create multiple events to prevent having our system bogged down and to not spam the activity feed.

Screenshots

Admin setting

Before

After

Activity feed

Before

After

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• 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

#31007 (closed)