Redis HLL counters on plan/namespace level [RUN AS-IF-FOSS]

What does this MR do?

Adds method track_event_in_context(value, event_name, context, time = Time.zone.now) to track event on context level, allowed context is default, free, bronze, silver, gold, starter, premium, ultimate.

Add docs

Track events

• track_event_in_context(value, event_name, context, time = Time.zone.now)
• we track events for given context if context is present and valid.

Getting the counts

unique_events(value, event_name, context, time = Time.zone.now)

• if context is blank we return the value track for the event

• if context is valid(one of allowed values) we return the unique_events for the specific event for given context

• if context is invalid(not in allowed list) we raise error

Next steps

We might consider adding

• a method to count unique events for given context
• a method to get the total count unique events for all contextes for a given event

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 #254669 (closed)