Improve metrics definition generator for Redis HLL counters

When adding tracking using Redis HLLL, we automatically add the corresponding events in USage Ping json payload.

For each event added under known_events/ we generate 2 counter having suffix _weekly, _monthly

Docs https://docs.gitlab.com/ee/development/usage_ping.html#known-events-are-added-automatically-in-usage-data-payload

We could improve the YAML metrics definition generator to generate the correct 2 metrics files for given event name