Create common solution on how to count and track feature flag enabled value

Problem

For groupobservability needs to find out , number of customers with FF enabled (a "customer" = a top-level group/namespace , should differentiate dogfood vs customers)

This is good opportunity for us to implement generic solution where in future we can just reuse the logic.

Reference MR - !81311 (diffs)

Desired Outcome

We should be able to track all the enabled feature flags suing Service Ping

Potential Solution

Explore if we already have a generic solution for this or if we need to create one.

Can use a similar API functionality as an example https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/api/features.rb#L60-60