Resolve "Implement redis based package events tracking"

What does this MR do?

Adds the PackageUniqueCounter class to count unique package events. The class inherits from HLLRedisCounter in order to eliminate the need to define the events in a .yml file as required by HLLRedisCounter. We have too many events introduces and adding to a yml file would be inefficient.

This class will be hooked to the packages API to track the events in a follow up MR as well as hooking it to usage data to report the values.

Screenshots (strongly suggested)

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

Related to #275942 (closed)