Add service ping context to ecosystem_total_unique_counts_monthly

What does this MR do and why?

This MR adds Service Ping context to redis_hll_counters.ecosystem.ecosystem_total_unique_counts_monthly metric for Data team.

Custom context is added according to https://docs.gitlab.com/ee/development/snowplow/schemas.html#gitlab_service_ping context schema.

Screenshots or screen recordings

No UI changes

How to set up and validate locally

How to test Slack events

How to test Jira events

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #382416 (closed)