Integrate Product Analytics with Internal Events for frontend on Gitlab.com

Problem

After integrating the Browser SDK with Gitlab.com in https://gitlab.com/gitlab-org/gitlab/-/issues/415554 we are only sending PageView data but no actual events (e.g. for button clicks). For the time being we anticipate that stakeholders will want to use Product Analytics alongside the existing tracking and visualisation (e.g. Sisense) while Product Analytics starts to cover all use-cases. We do not want to create confusion and additional work for developers by introducing additional methods for ProductAnalytics, that have to be called in addition to existing event tracking.

Desired Outcome

Whenever an event is tracked with Gitlab's Internal Events tracking on the Frontend it should be sent to Product Analytics in addition to the other endpoints. Setup:

Proposed Solution

1. Instrument the function that currently sends to the main Snowplow cluster to send to Product Analytics as well.
2. Make sure we do not send any additional PII data (e.g. user_id) while #415555 (closed) is not in place.